2024-03-28T17:31:45Z
http://docs.lib.purdue.edu/do/oai/
oai:docs.lib.purdue.edu:nanopub-1000
2007-02-22T19:04:04Z
publication:dp
publication:engr
publication:nanopub
publication:nano
publication:ece
publication:ecepubs
Direct current electrical characterization of ds-DNA in nanogap junctions
Iqbal, Samir Muzaffar
Balasundaram, G.
Ghosh, Subhasis
Bergstrom, Donald E
Bashir, Rashid
Measurements of DNA conductivity, hybridization, and melting using electronic means can have wide applications in molecular electronics and biological sensors. We have fabricated nanogap break-junctions by electromigration through thin gold-on-titanium films. 18-mer thiolated ds-DNA molecules were covalently attached between the electrodes and dc electrical measurements were done. The conductance was measured through the molecule before and after a temperature ramp from 300 to 400 K. A dramatic decrease in conductance was observed, analogous to an electrical fuse, possibly attributed to complete or partial denaturing of the ds-DNA molecules bridging the nanogaps. We also show evidence that the dc resistance of dry DNA strands of the same length decreases with increasing guanine-cytosine content in the sequence with values ranging from 10 M ! to 2 G !. These findings can have important consequences in DNA-based molecular
2005-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/1
https://docs.lib.purdue.edu/context/nanopub/article/1000/viewcontent/Bashir_001.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1001
2019-05-31T15:28:29Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Heterogeneous integration of CdS filters with GaN LEDs for fluorescence detection microsystems
Chediak, J. Alex
Luo, Zhongsheng
Seo, Jeonggi
Cheung, Nathan
Lee, Luke P
Sands, Timothy D.
Microassembly of a hybrid fluorescence detection microsystem by heterogeneous integration of a CdS thin-film filter, an (In, Ga)N thin-film blue LED, and a disposable PDMS microfluidic device onto a Si PIN photodetector substrate is described. The CdS thin film filter was deposited directly onto a photodetector by pulsed-laser deposition. A thin-film (In, Ga)N LED was then transferred by a novel “pixel-to-point” laser lift-off process from the sapphire growth substrate to the silicon photodetector substrate. The final integration step was achieved by positioning a disposable polymer microfludic device onto the excitation/detection subsystem. Pixel-to-point transfer is potentially an enabling microassembly process for the fabrication of multicolor fluorescence-based bioassays and chemical detection microsystems.
2003-07-01T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/11
https://doi.org/10.1016/j.sna.2003.10.015
Birck and NCN Publications
Purdue University
Heterogeneous integration
Fluorescence detection
Optical thin film filter
Microsystem
Pixel-to-point transfer
oai:docs.lib.purdue.edu:nanopub-1002
2019-06-06T13:57:25Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Dendrimer-assisted low-temperature growth of carbon nanotubes by plasma-enhanced chemical vapor deposition
Amama, Placidus B
Ogebule, Oluwaseyi
Maschmann, Matthew R.
Sands, Timothy D.
Fisher, Timothy S.
Using a shielded growth approach and N2-annealed, nearly monodispersed Fe2O3 nanoparticles synthesized by interdendritic stabilization of Fe3+ species within fourth-generation poly(amidoamine) dendrimers, carbon nanotubes and nanofibers were successfully grown at low substrate temperatures (200-400 degreesC) by microwave plasma-enhanced chemical vapor deposition.
2006-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/12
http://xlink.rsc.org/?DOI=b602623k
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1004
2019-06-06T14:00:41Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Hydrodynamic coupling between micomechanical beams osciallating in viscous fluids
Basak, Sudipta
Raman, Arvind
We analyze the hydrodynamic coupling between long, slender micromechanical beams microbeams
2007-03-05T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/13
https://doi.org/10.1063/1.2423254
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1003
2019-06-06T13:59:16Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Effects of a carbon nanotube layer on electrical contact resistance between copper substrates
Park, Myounggu
Cola, Baratunde A
Siegmund, Thomas
Xu, Jun
Maschmann, Matthew R.
Fisher, Timothy S.
Kim, Hyonny
2006-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/47
https://doi.org/10.1088/0957-4484/17/9/038
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1005
2007-03-13T14:31:03Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Measuring the Interaction Force Between a Tip and a Substrate Using a Quartz Tuning Fork Under Ambient Conditions
Qin, Yexian
Reifenberger, R.
Tuning forks mounted with sharp tips provide an alternate method to silicon microcantilevers for probing the tip-subsrate interaction in scanning probe microscopy. The high quality factor and stable resonant frequency of the tuning fork allow accurate measurements of small shifts in the resonant frequency as the tip approaches the substrate. To permit an accurate measure of surface interaction forces, the electrical and piezomechanical properties of a tuning fork has been characterized using techniques derived from scanning probe microscopy. After proper calibration, representative interaction force data for a conventional Si tip and an HOPG substrate are obtained under ambient conditions.
2006-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/14
https://docs.lib.purdue.edu/context/nanopub/article/1005/viewcontent/Reifenberger_001.pdf
Birck and NCN Publications
Purdue University
Scanning Probe
Quartz Tuning Fork
Interaction Force
oai:docs.lib.purdue.edu:nanopub-1006
2019-06-06T14:05:10Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Detection of Folate Binding Protein with Enhanced Sensitivity Using a Functionalized Quartz Crystal Microbalance Sensor
Henne, Walter A.
Doorneweerd, Derek D.
Lee, Joonhyung
Low, Philip S.
Savran, Cagri
In this report, we describe the development of a quartz crystal microbalance biosensor for detection of folate binding protein (FBP). Using a simple folate—BSA conjugate absorbed onto a Au-coated quartz sensor, a detection limit of 30 nM was achieved. Binding of FBP to the sensor surface could be blocked at concentrations as high as 1 uM with a 100-fold excess of folic acid, indicating the specificity of the folate—FBP interaction and the absence of nonspecific binding to the functionalized surface. Moreover, capture could be achieved in the presence of blood serum, making the assay amendable to the analysis of bodily fluids. Further signal enhancement based on an anti-FBP antibody and protein-A-coated gold nanosphere sandwich assay extended the detection limit to 50 pM (~3 orders-of-magnitude improvement). Given the overexpression of FBP in certain malignancies and inflammatory disorders, we expect the methodology described here to be useful to detect FBP as a possible biomarker for disease diagnosis.
2006-07-15T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/46
https://doi.org/10.1021/ac060324r
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1007
2007-03-13T14:27:00Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Enhancement of spontaneous and stimulated emission of a rhodamine 6G dye by an Ag aggregate
Noginov, M. A.
Zhu, G.
Bahoura, M.
Small, C. E.
Davison, C.
Adegoke, J.
Drachev, V. P.
Nyga, P.
Shalaev, V. M.
We have demonstrated that by adding the solution of aggregated silver nanoparticles to the solution of rhodamine 6G dye, one can enhance the efficiency of spontaneous and stimulated emission. We attribute an increase of the spontaneous emission intensity of dye to the increase of the absorption efficiency caused by the field enhancements in metallic nanostructures associated with surface plasmons. The enhancement of the stimulated emission of dye, which has the same nature as the enhancement of absorption, was observed in the pump-probe and laser experiments.
2006-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/10
https://docs.lib.purdue.edu/context/nanopub/article/1007/viewcontent/Shalaev_002.pdf
Birck and NCN Publications
Purdue University
spontaneous emission
absorption
stimulated emission
oai:docs.lib.purdue.edu:nanopub-1009
2019-06-06T14:08:34Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
A Design for Combining Biological and Semiconductor Cleanrooms for Nanotechnology Research
Weaver, John R.
Nanotechnology brings together various functional areas for interdisciplinary research, making it necessary for them to reside in a single facility. The conjoining of biology, biomedical engineering, and bio-nano-micro-electro-mechanical systems (MEMS) with semiconductor and MEMS processing requires that these technologies coexist in ultraclean facilities, while the facility designs and operating practices are incompatible. This case study describes a design concept in a collaborative research environment that meets biocleanliness goals and International Organization for Standardization (ISO) Class 4 particle concentrations (as defined in ISO 14644-1, Cleanrooms and associated controlled environments – Part 1: Classification of air cleanliness).
2005-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/8
https://doi.org/10.17764/jiet.48.1.u511tw1843710824
Birck and NCN Publications
Purdue University
Nanotechnology
facility design
cleanroom design
biological cleanroom
semiconductor cleanroom
university
oai:docs.lib.purdue.edu:nanopub-1008
2019-06-06T14:06:56Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Alpha-synuclein as a template for the synthesis of metallic nanowires
Padalkar, S
Hulleman, J
Deb, P
Cunzeman, K
Rochet, J C
Stach, E A
Stanciu, L
Exploiting the concepts learnt from nature to build new nanomaterials from the bottom up is critical for the efficient design of complex nanodevices. We demonstrate for the first time that the capacity of the alpha-synuclein protein to assemble into nanofibres can be used for the synthesis of metallic nanowires. Silver and platinum nanowires with controlled diameters, ranging from 15 to 125 nm, have been synthesized on an alpha-synuclein protein fibre scaffold.
2007-03-05T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/9
https://doi.org/10.1088/0957-4484/18/5/055609
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1017
2007-03-13T14:24:21Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Parametric resonance based scanning probe microscopy
Moreno-Moreno, M.
Raman, Arvind
Gomez-Herrero, J.
Reifenberger, R.
We propose a mode of dynamic scanning probe microscopy based on parametric resonance for highly sensitive nanoscale imaging and force spectroscopy. In this mode the microcantilever probe is excited by means of a closed-loop electronic circuit that modulates the microcantilever stiffness at a frequency close to twice its natural resonance frequency. Under ambient conditions this parametric pumping leads to self-sustained oscillations in a narrow frequency bandwidth thereby resulting in exquisitely sharp, controllable, and non-Lorentzian resonance peaks. We discuss and demonstrate the potential of imaging and force spectroscopy using this mode.
2006-07-27T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/15
https://docs.lib.purdue.edu/context/nanopub/article/1017/viewcontent/Reifenberger_004.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1011
2019-06-06T13:42:59Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Current-transport properties of atomic-layer-deposited ultrathin Al2O3
Lin, H. C.
Ye, P. D.
Wilk, G. D.
We report detailed current-transport studies of ultrathin Al2O3 dielectrics on GaAs grown by atomic layer deposition (ALD) as a function of film thickness, ambient temperature and electric field. The leakage current in ultrathin Al2O3 on GaAs is comparable to or even lower than that of the state-of-the-art SiO2 on Si, not counting on high dielectric constant for Al2O3. By measuring leakage cur- rent at a wide range of temperatures from 133 K to 475 K, we are able to identify the electron transport mechanism and measure the thermal-activation energy of the ultrathin oxide films. This thermal-activation energy is proposed as a parameter to generally character- ize the quality of ultrathin dielectrics on semiconductors.
2006-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/44
https://doi.org/10.1016/j.sse.2006.04.021
Birck and NCN Publications
Purdue University
Atomic layer deposition
GaAs MOSFET
Thermal-activation energy
oai:docs.lib.purdue.edu:nanopub-1010
2019-06-06T13:34:59Z
publication:dp
publication:engr
publication:chempubs
publication:chem
publication:nano
publication:nanopub
publication:ece
publication:sci
publication:ecepubs
Sulfide-Arrested Growth of Gold Nanorods
Zweifel, Daniel A.
Wei, Alexander
The growth of gold nanorods can be arrested at intermediate stages by treatment with Na2S, providing greater control over their optical resonances. Nanorods prepared by the seeded reduction of AuCl4 in aqueous cetyltrimethylammonium bromide solutions in the presence of AgNO3 typically exhibit a gradual blueshift in longitudinal plasmon resonance, over a period of hours to days. This “optical drift” can be greatly reduced by adding millimolar concentrations of Na2S to quench nanorod growth, with an optimized sulfur:metal ratio of 4:1. The sulfide-treated nanorods also experience a marked redshift as a function of Na2S concentration to produce stable plasmon resonances well into the near-infrared. Sulfide treatment permitted a time-resolved analysis of nanorod growth by transmission electron microscopy, revealing two distinct periods: an initial growth burst (t < 15 min) that generates dumbbell-shaped nanorods with flared ends and a slower phase (t > 30 min) favoring growth around the midsection, leading to nanorods with the more familiar oblate geometry. The blueshift in plasmon resonance that accompanies the dumbbell- to-oblate shape transition correlates more strongly with changes in the length-to-midsection (L/D1) ratio rather than the length-to-end width (L/D2) ratio, based on the empirical relationship introduced by El- Sayed and co-workers (Link, S.; Mohamed, M. B.; El-Sayed, M. A. J. Phys. Chem. B 1999, 103, 3073- 3077).
2005-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/45
https://doi.org/10.17764/jiet.48.1.u511tw1843710824
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1014
2019-06-06T14:10:43Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
3-Omega Measurements of Vertically Oriented Carbon Nanotubes on Silicon
Hu, X. Jack
Padilla, Antonio A.
Xu, Jun
Fisher, Timothy S.
Goodson, Kenneth E.
An exploratory thermal interface structure, made of vertically oriented carbon nanotubes directly grown on a silicon substrate, has been thermally characterized using a 3-omega method. The effective thermal conductivities of the carbon nanotubes (CNT) sample, including the effects of voids, are found to be 74 W/mK to 83 W/mK in the temperature range of 295K to 323K, one order higher than that of the best thermal greases or phase change materials. This result suggests that the vertically oriented CNTs potentially can be a promising next-generation thermal interface solution. However, fairly large thermal resistances were observed at the interfaces between the CNT samples and the experimental contact. Minimizing these contact resistances is critical for the application of these materials.
2006-11-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/5
https://doi.org/10.1115/1.2352778
Birck and NCN Publications
Purdue University
thermal conductivity
contact thermal resistance
carbon nanotube
thermal interface material
3-omega method
thermal management
oai:docs.lib.purdue.edu:nanopub-1013
2019-06-06T13:54:45Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Conductivity and pH Dual Detection of Growth Prfile of Healthy and Stressed Listeria monocytogenes
Yang, Liju
Banada, Padmapriya P
Liu, Yi-Shao
Bhunia, Arun K
Bashir, Rashid
In this study, growth of Listeria monocytogenes in a low conductivity growth medium (LCGM) was simulaneously monitored by conductivity and pH measurements. Detection times obtained from the conductivity and pH growth curves were inversely related to the initial concentration of L. monocytogenes in the medium. Linear responses were found by plotting detection times obtained from both conductivity and pH growth curves as a function of initial cell concentration in the range of 10^2 to 10^7 cfu/mL. The detection time was approximately 12 and 2 h for 10^2 and 10^7 cfu/mL of viable L. monocytogenes, respectively, using the conductivity growth curves, whereas it was approximately 1 h less using the pH growth curves. This dual detection system was used for valuating the growth of acid-, temperature-, and salt-treated L. monocytogenes in the medium. Acid stress at pH 2 and 3 for 3 h caused approximately 12 and 4 h delay in the detection time on pH growth curves, while stress at pH 5 for 3 h did not cause a significant delay in detection time. Delay in detection times was also observed for L. monocytogenes cells exposed to 45 degrees C for more than 1 h (2 and 6 h). Exposure to 10% NaCI for 3 h did not cause visible delay in the detection time. These observations on detection times for stressed L. monocytogenes had a consistent trend with the cell number decrease determined by surface plating method.
2005-09-15T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/6
https://doi.org/10.1002/bit.20642
Birck and NCN Publications
Purdue University
pH
conductivity
detection
Listeria monocytogenes
stressed bacteria
oai:docs.lib.purdue.edu:nanopub-1015
2019-07-01T15:16:58Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Fabrication and characterization of solid-state nanopores using a field emission scanning electron microscope
Chang, Hung
Iqbal, Samir
Stach, E A
King, Alexander H.
Zaluzec, Nestor J.
Bashir, Rashid
The fabrication of solid-state nanopores using the electron beam of a transmission electron microscope
2006-04-17T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/4
https://doi.org/10.1063/1.2179131
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1012
2019-06-06T13:47:27Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Carbon incorporation during ethene oxidation on Pd(111) studied by in situ X-ray photoelectron spectroscopy at 2 x 10-3 mbar
Gabasch, Harald
Kleimenov, Evgueni
Teschner, Detre
Zafeiratos, Spiros
Hävecker, Michael
Knop-Gericke, Axel
Schlögel, Robert
Zemlyanov, Dmitry
Aszalos-Kiss, Balazs
Hayek, Konrad
Klötzter, Bernhard
The oxidation of ethene on the Pd(111) surface was studied in the temperature range of 330–923 K by in situ XPS and mass spectrometry during both heating and cooling in a reaction mixture of 5
2006-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/7
http://dx.doi.org/10.1016/j.jcat.2006.06.022
Birck and NCN Publications
Purdue University
Palladium
Pd(111)
Ethene oxidation
High pressure in situe XPS
Subsurface carbon
dissolved carbon
termperature-programmed reation
Kinetic hysteresis
oai:docs.lib.purdue.edu:nanopub-1018
2019-06-06T14:12:07Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Equilibrium limits of coherency in strained nanowire heterostructures
Ertekin, Elif
Greaney, P. A.
Chrzan, D. C.
Sands, Timothy D
2005-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/2
https://doi.org/10.1063/1.1903106
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1019
2019-06-06T14:13:27Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Vertical single- and double-walled carbon nanotubes grown from modified porous anodic alumina templates
Maschmann, Matthew R
Franklin, Aaron D
Amama, Placidus B
Zakharov, D N
Stach, E A
Sands, Timothy D
Fisher, Timothy S.
Vertical single-walled and double-walled carbon nanotube (SWNT and DWNT) arrays have been grown using a catalyst embedded within the pore walls of a porous anodic alumina (PAA) template. The initial film structure consisted of a SiOx adhesion layer, a Ti layer, a bottom Al layer, a Fe layer, and a top Al layer deposited on a Si wafer. The Al and Fe layers were subsequently anodized to create a vertically oriented pore structure through the film stack. CNTs were synthesized from the catalyst layer by plasma-enhanced chemical vapour deposition (PECVD). The resulting structure is expected to form the basis for development of vertically oriented CNT-based electronics and sensors.
2006-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/23
https://doi.org/10.1088/0957-4484/17/15/052
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1020
2019-06-06T14:32:00Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Enhancement of surface plasmons in an Ag aggregate by optical gain in a dielectric medium
Noginov, M. A.
Zhu, G.
Bahoura, M.
Adegoke, J.
Small, C. E.
Ritzo, B. A.
Drachev, V. P.
Shalaev, V. M.
We have observed the compensation of loss in a metal by a gain in a dielectric medium in the mixture of an Ag aggregate and a Rhodamine 6G dye. The demonstrated sixfold enhancement of the Rayleigh scattering is the evidence of the enhancement of the surface-plasmon resonance. The reported experimental observation facilitates many applications of nanoplasmonics.
2006-10-15T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/22
https://doi.org/10.1364/OL.31.003022
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1022
2019-06-06T14:33:22Z
publication:dp
publication:engr
publication:chempubs
publication:chem
publication:nano
publication:nanopub
publication:ece
publication:sci
publication:ecepubs
Calixarene-encapsulated nanoparticles: self-assembly into functional nanomaterials
Wei, Alexander
Calixarenes are excellent surfactants for enhancing the dispersion and self-assembly of metal nanoparticles into well-defined structures, particularly those with unit length scales in the 10–100 nm size range. Particles within these ensembles are strongly coupled, giving rise to unique collective optical or magnetic properties. The self-assembled nanostructures described in this feature article include 2D arrays of colloidal Au nanoparticles with size-dependent plasmonic responses, and sub-100 nm Co nanoparticle rings with chiral magnetic states. These nanoparticle assemblies may be further developed for applications in chemical sensing based on surfaceenhanced Raman scattering (SERS) and as binary elements for nonvolatile memory, respectively.
2006-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/20
https://doi.org/10.1039/B515806K
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1023
2019-06-06T14:34:40Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Self-heating simulation of GaN-based metal-oxide-semiconductor high-electron-mobility transistors including hot electron and quantum effects
Xu, W. D.
Chen, X. S.
Quan, Z. J.
Xia, C. S.
Lu, W.
Ye, P. D.
Undoped GaN-based metal-oxide-semiconductor high-electron-mobility transistors !MOS-HEMTs" with atomic-layer-deposited Al2O3 gate dielectrics are fabricated with gate lengths from 1 up to 40 !m. Using a two-dimensional numerical simulator, we report the results of self-heating simulations of the GaN-based MOS-HEMTs, including hot electron and quantum effects. The simulated electrical characteristics are in good agreement with reported experimental data. The effect of the gate and source/drain extension lengths on both the output performance and self-heating is discussed in detail, allowing for device optimization. The dissipated Joule electric power causes the self-heating effects, which lead to negative differential output conductance. Our results demonstrate that the hot electrons make a negligible contribution to the negative differential output conductance in our long channel MOS-HEMTs. In order to investigate their joint interactions to the MOS-HEMT’s operation, the different static interface trap and charge densities created at the AlGaN/Al2O3 interface are considered in the output characteristics. Results show that the presence of the interface charges and traps are directly responsible for the observed current collapse and device switching in the GaN-based MOS-HEMTs. The self-heating is also strongly affected due to the fluctuation of the interface states.
2006-11-29T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/19
https://doi.org/10.1063/1.2354327
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1025
2019-06-06T14:35:59Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Thermionic emission from surface-terminated nanocrystalline diamond
Robinson, Vance S.
Show, Yoshiyuki
Swain, Greg M.
Reifenberger, R.
Fisher, Timothy S.
Thermionic electron emission forms the basis of both electron sources for a variety of applications and a direct energy conversion process that is compact and scalable. The present study characterizes thermionic emission from boron-doped nanocrystalline diamond films with hydrogen and nitrophenyl surface termination layers. A hemispherical energy analyzer was used to measure electron energy distributions from the emitters at elevated temperatures. Thermionic emission energy distributions, acquired at temperatures ranging from 700 to 1100°C, reveal that emission occurs from regions of differing work functions. The relative peak intensities, representing each work function, change with temperature indicating instability in the emitter's surface chemistry. Corresponding partial pressure measurements of pertinent gases present in the chamber during the experiment were collected by a residual gas analyzer and support the hypothesis of unstable surface chemistry. The lowest work functions measured for the hydrogen- and nitrophenyl-terminated films were 3.95 and 3.88eV, respectively. After the initial heating cycle, the hydrogenterminated sample's surface was regenerated by exposure to hydrogen plasma. The lower work function was restored by this process, and the resulting thermionic electron energy distributions again were indicative of surface desorption.
2006-10-01T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/17
https://doi.org/10.1016/j.diamond.2006.01.017
Birck and NCN Publications
Purdue University
Thermionic emission; Nanocrystalline diamond; Electron energy analyzer; Surface termination
oai:docs.lib.purdue.edu:nanopub-1026
2019-06-06T14:38:34Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
DNA counterion current and saturation examined by a MEMS-based solid state nanopore sensor
Chang, Hung
Venkatesan, Bala Murali
Iqbal, Samir Muzaffar
Andreadakis, G.
Kosari, F.
Vasmatzis, G.
Peroulis, Dimitrios
Bashir, Rashid
Reports ofDNAtranslocation measurements have been increasing rapidly in recent years due to advancements in pore fabrication and these measurements continue to provide insight into the physics of DNA translocations through MEMS based solid state nanopores. Specifically, it has recently been demonstrated that in addition to typically observed current blockages, enhancements in current can also be measured under certain conditions. Here, we further demonstrate the power of these nanopores for examining single DNA molecules by measuring these ionic currents as a function of the applied electric field and show that the direction of the resulting current pulse can provide fundamental insight into the physics of condensed counterions and the dipole saturation in single DNA molecules. Expanding on earlier work by Manning and others, we propose a model of DNA counterion ionic current and saturation of this current based on our experimental results. The work can have broad impact in understanding DNA sensing, DNA delivery into cells, DNA conductivity, and molecular electronics.
2006-06-23T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/16
https://doi.org/10.1007/s10544-006-9144-x
Birck and NCN Publications
Purdue University
Nanopore . DNA counterions . Single molecule
oai:docs.lib.purdue.edu:nanopub-1033
2007-03-13T13:56:35Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Ultrasensitive mass sensing using mode localization in coupled microcantilevers
Spletzer, Matthew
Raman, Arvind
Wu, Alexander Q.
Xu, Xianfan
Reifenberger, R.
We use Anderson or vibration localization in coupled microcantilevers as an extremely sensitive method to detect the added mass of a target analyte. We focus on the resonance frequencies and eigenstates of two nearly identical coupled gold-foil microcantilevers. Theoretical and experimental results indicate that the relative changes in the eigenstates due to the added mass can be orders of magnitude greater than the relative changes in resonance frequencies. Moreover this sensing paradigm possesses intrinsic common mode rejection characteristics thus providing an alternate way to achieve ultrasensitive mass detection under ambient conditions.
2006-06-27T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/37
https://docs.lib.purdue.edu/context/nanopub/article/1033/viewcontent/Raman_005.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1028
2019-06-06T14:44:13Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Very high-cycle fatigue failure in micron-scale polycrystalline silicon films: Effects of envrionment and surface oxide thickness
Alsem, D. H.
Timmerman, R.
Boyce, B. L.
Stach, E A
De Hosson, J. Th. M.
Ritchie, R. O.
Fatigue failure in micron-scale polycrystalline silicon structural films, a phenomenon that is not observed in bulk silicon, can severely impact the durability and reliability of microelectromechanical system devices. Despite several studies on the very high-cycle fatigue behavior of these films
2007-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/42
https://doi.org/10.1063/1.2403841
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1027
2007-05-08T16:40:10Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Dislocation Dynamics in Nanocrystalline Nickel
Shan, Z. W.
Wiezorek, J. M. K.
Stach, E A
Follstaedt, D. M.
Knapp, J. A.
Mao, S. X.
It is believed that the dynamics of dislocation processes during the deformation of nanocrystalline materials can only be visualized by computational simulations. Here we demonstrate that observations of dislocation processes during the deformation of nanocrystalline Ni with grain sizes as small as 10 nm can be achieved by using a combination of in situ tensile straining and high-resolution transmission electron microscopy. Trapped unit lattice dislocations are observed in strained grains as small as 5 nm, but subsequent relaxation leads to dislocation recombination.
2007-03-02T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/43
https://docs.lib.purdue.edu/context/nanopub/article/1027/viewcontent/Stach_006.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1031
2019-06-06T14:48:27Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Chaos in Atomic Force Microscopy
Hu, Shuiqing
Raman, Arvind
Chaotic oscillations of microcantilever tips in dynamic atomic force microscopy (AFM) are reported and characterized. Systematic experiments performed using a variety of microcantilevers under a wide range of operating conditions indicate that softer AFM microcantilevers bifurcate from periodic to chaotic oscillations near the transition from the noncontact to the tapping regimes. Careful Lyapunov exponent and noise titration calculations of the tip oscillation data confirm their chaotic nature. AFM images taken by scanning the chaotically oscillating tips over the sample show small, but significant metrology errors at the nanoscale due to this ‘‘deterministic’’ uncertainty.
2006-01-27T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/39
http://dx.doi.org/10.1103/PhysRevLett.96.036107
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1029
2007-05-08T16:36:38Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Low-frequency noise statistics for the breakdown characterization of ultrathin gate oxides
Butt, N. Z.
Chang, A. M.
Raza, H.
Bashir, Rashid
Liu, J.
Kwong, D. L.
We have investigated the statistics of low-frequency noise in the tunneling current of ultrathin oxides
2006-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/41
https://docs.lib.purdue.edu/context/nanopub/article/1029/viewcontent/Bashir_005.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1036
2019-06-06T15:19:04Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
High-Reflectivity A1-Pt Nanostructured Ohmic Contact to p-GaN
Kim, Ho Young
Deb, P
Sands, Timothy D
The effect of nanoscale Pt islands on the electrical characteristics of contacts to p-type gallium nitride (GaN) has been investigated to explore the feasibility for the flip-chip configuration light-emitting diodes (LEDs) using an A1-based reflector. An as-deposited A1 contact to p-GaN with a net hole concentration of 3x10^17 cm^-3 was rectifying. However, an A1 contact with nanoscale Pt islands at the interface exhibited ohmic behavior. A specific contact resistivity of 2.1x10^-3 ohm•cm^2 and a reflectance of 84% at 460 nm were measured for the A1 contact with nanoscale Pt islands. Current-voltage temperature measurements revealed a Schottky barrier height reduction from 0.80 eV for the A1 contact to 0.58 eV for the A1 contact with nanoscale Pt islands. The barrier height reduction may be attributed to electric field enhancement and the enhanced tunneling due to the presence of the nanoscale Pt islands. This will offer an additional silver-free option for the p-type ohmic contact in flip-chip configuration LEDs. Theory suggests that the ohmic contact characteristics may be improved further with smaller Pt islands that will enhance tunneling across the interface with the GaN and in the vicinity of the Pt-A1 interface.
2006-10-01T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/34
https://doi.org/10.1109/TED.2006.882287
Birck and NCN Publications
Purdue University
Contact resistivity
flip-chip configuration
Pt islands
Schottky barrier height (SBH)
tunneling
oai:docs.lib.purdue.edu:nanopub-1035
2019-06-06T15:17:59Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Equilibrium Analysis of Lattice-Mismatched Nanowire Heterostructures
Ertekin, E.
Greaney, P. A.
Sands, Timothy D
Chrzan, D. C.
The quality of lattice-mismatched semiconductor heterojunctions is often limited by the presence of misfit dislocations. Nanowire geometries offer the promise of creating highly mismatched, yet dislocation free heterojunctions. A simple model, based upon the critical thickness model of Matthews and Blakeslee for misfit dislocation formation in planar heterostructures, illustrates that there exists a critical nanowire radius for which a coherent heterostructured nanowire system is unstable with respect to the formation of misfit dislocations. The model indicates that within the nanowire geometry, it should be possible to create perfect heterojunctions with large lattice-mismatch.
2003-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/35
https://doi.org/10.1557/PROC-737-F10.4
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1034
2019-06-06T14:55:47Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Hydrodynamic loading of microcantilevers vibrating in viscous fluids
Basak, Sudipta
Raman, Arvind
Garimella, Suresh
The hydrodynamic loading of elastic microcantilevers vibrating in viscous fluids is analyzed computationally using a three-dimensional, finite element fluid-structure interaction model. The quality factors and added mass coefficients of several modes are computed accurately from the transient oscillations of the microcantilever in the fluid. The effects of microcantilever geometry, operation in higher bending modes, and orientation and proximity to a surface are analyzed in detail. The results indicate that in an infinite medium, microcantilever damping arises from localized fluid shear near the edges of the microcantilever. Closer to the surface, however, the damping arises due to a combination of squeeze film effects and viscous shear near the edges. The dependence of these mechanisms on microcantilever geometry and orientation in the proximity of a surface are discussed. The results provide a comprehensive understanding of the hydrodynamic loading of microcantilevers in viscous fluids and are expected to be of immediate interest in atomic force microscopy and microcantilever biosensors.
2006-07-28T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/36
https://doi.org/10.1063/1.2202232
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1040
2007-03-13T15:48:05Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
High-performance GaAs metal-insulator-semiconductor field-effect transistors enabled by self-assembled nanodielectrics
Lin, H. C.
Ye, P. D.
Xuan, Y.
Lu, G.
Facchetti, A.
Marks, T. J.
High-performance GaAs metal-insulator-semiconductor field-effect-transistors
2006-10-12T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/30
https://docs.lib.purdue.edu/context/nanopub/article/1040/viewcontent/Ye_008.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1037
2019-06-06T15:20:13Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Growth of TiN/GaN metal/semiconductor multilayers by reactive pulsed laser deposition
Rawat, Vijay
Sands, Timothy D
TiN / GaN metal/semiconductor multilayers were grown by reactive pulsed laser deposition in an ammonia ambient on sapphire and MgO substrates for potential application in solid-state thermionic direct energy conversion devices. Crystallographic analysis of the multilayers by high-resolution x-ray diffraction and cross-sectional transmission electron microscopy revealed that, despite the difference in the crystal structures of rocksalt TiN and wurtzite GaN, it is possible to grow thick
2006-09-29T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/33
https://doi.org/10.1063/1.2337784
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1041
2007-03-13T15:52:24Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Minority-carrier characteristics of InGaAs metal-oxide-semiconductor structures using atomic-layer-deposited A12O3 gate dielectric
Xuan, Y.
Ye, P. D.
Lin, H. C.
Wilk, G. D.
Atomic layer deposition
2006-10-12T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/29
https://docs.lib.purdue.edu/context/nanopub/article/1041/viewcontent/Ye_009.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1039
2007-03-13T15:41:15Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Capacitance-voltage studies on enhancement-mode InGaAs metal-oxide-semiconductor field-effect transistor using atomic-layer-deposited AI2O3 gate dielectric
Xuan, Y.
Lin, H. C.
Ye, P. D.
Wilk, G. D.
Atomic layer deposition
2006-06-30T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/31
https://docs.lib.purdue.edu/context/nanopub/article/1039/viewcontent/Ye_005.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1038
2019-06-06T15:21:11Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Optical negative-index metamaterials
Shalaev, V. M.
Artifi cially engineered metamaterials are now demonstrating unprecedented electromagnetic properties that cannot be obtained with naturally occurring materials. In particular, they provide a route to creating materials that possess a negative refractive index and offer exciting new prospects for manipulating light. This review describes the recent progress made in creating nanostructured metamaterials with a negative index at optical wavelengths, and discusses some of the devices that could result from these new materials.
2006-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/32
https://doi.org/10.1038/nphoton.2006.49
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1043
2019-07-01T15:29:56Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Reliable fabrication method of transferable micron scale metal pattern for poly(dimethylsiloxane) metallization
Lim, Kwan Seop
Chang, Woo-Jin
Koo, Yoon-Mo
Bashir, Rashid
We have developed a reliable fabrication method of forming micron scale metal patterns on poly(dimethylsiloxane) (PDMS) using a pattern transfer process. A metal stack layer consisting of Au–Ti–Au layers, providing a weak but reliable adhesion, was deposited on a silicon wafer. The metal stack layer was then transferred to a PDMS substrate using serial and selective etching. We demonstrate that features as small as 2 mm were reliably transferred on to the PDMS substrate for use as interconnects and electrodes for biosensors and flexible electronics application.
2006-03-10T08:00:00Z
text
https://docs.lib.purdue.edu/nanopub/27
https://doi.org/10.1002/adma.200501048
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1042
2019-06-06T15:22:17Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
In situ XPS study of Pd(111) oxidation at elevated pressure, Part 2: Palladium oxidation in the 10^1 mbar range
Gabasch, Harald
Unterberger, Werner
Hayek, Konrad
Klötzer, Bernhard
Kleimenov, Evgueni
Teschner, Detre
Zafeiratos, Spiros
Hävecker, Michael
Knop-Gericke, Axel
Schlögl, Robert
Han, Jinyi
Ribeiro, Fabio H.
Aszalos-Kiss, Balazs
Curtin, Teresa
Zemlyanov, Dmitry
The oxidation of the Pd(1 1 1) surface was studied by in situ XPS during heating and cooling in 0.4 mbar O2. The in situ XPS data were complemented by ex situ TPD results. A number of oxygen species and oxidation states of palladium were observed in situ and ex situ. At 430 K, the Pd(1 1 1) surface was covered by a 2D oxide and by a supersaturated Oads layer. The supersaturated Oads layer transforms into the Pd5O4 phase upon heating and disappears completely at approximately 470 K. Simultaneously, small clusters of PdO, PdO seeds, are formed. Above 655 K, the bulk PdO phase appears and this phase decomposes completely at 815 K. Decomposition of the bulk oxide is followed by oxygen dissolution in the near-surface region and in the bulk. The oxygen species dissolved in the bulk is more favoured at high temperatures because oxygen cannot accumulate in the near-surface region and di
2006-05-09T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/28
http://dx.doi.org/10.1016/j.susc.2006.05.029
Birck and NCN Publications
Purdue University
X-ray photoelectron spectroscopy; Chemisorption; Oxidation; Surface chemical reaction; Palladium; Single crystal surfaces; Low index single
oai:docs.lib.purdue.edu:nanopub-1044
2019-07-01T15:31:17Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Enhanced Thermal Contact Conductance Using Carbon Nanotube Array Interfaces
Xu, Jun
Fisher, Timothy S.
Heat-conduction interfaces that employ carbon nanotube (CNT) arrays have been fabricated and studied experiementally using a reference calorimeter testing rig in a vacuum environment with infrared temperature measurements. Arrays of multiwalled CNTs are grown directly on silicon substrates with microwave plasma-enhanced chemical vapor deposition. Iron and nickel were used as CNT catalysts. CNT arrays grown under differnt synthesis conditions exhibit different pressure-contact conductance characteristics. The thermal contact resistance of CNTs with a copper interface exhibits promising results with a minimum value of 19.8 mm^2K/W at a pressure of 0.445 MPa.
2006-06-01T07:00:00Z
text
https://docs.lib.purdue.edu/nanopub/26
https://doi.org/10.1109/ITHERM.2004.1318332
Birck and NCN Publications
Purdue University
Carbon nanotubes (CNTs)
enhanced thermal contact conductance
microwave plasma enhanced chemical vapor deposition (PECVD)
oai:docs.lib.purdue.edu:nanopub-1045
2019-06-06T15:23:20Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Characterization of vaccinia virus particles using microscale silicon cantilever resonators and atomic force microscopy
Johnson, Luke
Gupta, Amit Kumar
Ghafoor, Azam
Akin, Demir
Bashir, Rashid
Rapid means of characterizing and detecting virus particles are very important for a wide variety of applications. We have used vaccinia virus, a member of the Poxviridae virus family and the basis of the smallpox vaccine, as the test case and characterized these particles using atomic force microscopy and micron-scale cantilever beams, with the long-term goal of developing devices for the direct rapid detection of air-borne virus particles. The cantilever beams, driven by thermal noise and a PZT piezoelectric ceramic, served as resonating sensors to measure the mass of these virus particles. Two different size cantilevers were used, with dimensions of 21
2005-10-13T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/24
https://doi.org/10.1016/j.snb.2005.08.047
Birck and NCN Publications
Purdue University
BioMEMS; Cantilever sensors; Resonant sensors
oai:docs.lib.purdue.edu:ocspub-1002
2007-03-26T18:43:16Z
publication:dp
publication:engr
publication:ocs
publication:nano
publication:nanopub
publication:ocspub
publication:ece
publication:ecepubs
Ambipolar conduction in transistors using solution grown InAs nanowires with Cd doping
Hang, Qingling
Wang, Fudong
Buhro, William E
Janes, David B
Nanowire field effect transistors have been fabricated using Cd doped InAs nanowires synthesized using a solution-liquid-solid technique. Both n-channel and p-channel characteristics have been observed, which implies that the surface Fermi level is not pinned in the conduction band. The observation of a p channel is attributed to the passivation of surface states by surface ligands introduced during nanowire synthesis and to the effects of heavy acceptor doping. Devices in which the surface ligands are removed by O-2 plasma treatment exhibit only n-channel conduction, which would be consistent with surface Fermi level pinning in the conduction band. (c) 2007 American Institute of Physics.
2007-03-26T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/ocspub/3
https://docs.lib.purdue.edu/context/ocspub/article/1002/viewcontent/Ambipolar_conduction_in_transistors_using_solution_grown_InAs.pdf
Oncological Sciences Center Publications
Purdue University
SEMICONDUCTOR NANOWIRES; ACCUMULATION; SURFACES
oai:docs.lib.purdue.edu:nanopub-1046
2019-06-10T13:14:37Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Nanoscale mechanisms of misfit dislocation propagation in undulated Si1-xGex/Si(100) epitaxial thin films
Wu, Chi-Chin
Stach, Eric A.
Hull, Robert
Nanoscale lateral variations in the stress field of undulated Si0.7Ge0.3/Si(100) films have been experimentally studied via in situ transmission electron microscopy annealing and through finite element calculations. When annealed at ~480 °C, misfit dislocations in a 30 nm film (having surface undulations of ~70 nm wavelength and ~3 nm amplitude) propagated at 80 nm s−1 average speed but with periodic variations from 0–30 nm s−1 at the peaks of the undulations to 160–240 nm s−1 at the troughs. A 2.0 GPa average film stress with variations from 3.2 to 4.4 GPa at the troughs to 0.7–1.2 GPa at the peaks is inferred from the observed dislocation velocities. These stress variations are significantly higher than those calculated from a finite element model of Si0.7Ge0.3/Si with the same surface geometry. Using standard models of dislocation kink dynamics, we have calculated how the effect of high stresses at the undulation troughs would be expected to enhance kink nucleation rates, and have found good agreement between our models and the experimentally observed range of dislocation velocities. These observations demonstrate the potential of probing the nanoscale structure in thin films through local variations of dislocation velocities.
2007-04-25T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/25
https://doi.org/10.1088/0957-4484/18/16/165705
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1047
2019-06-10T13:15:46Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Mechanisms for Fatigue of Micron-Scale Silicon Structural Films
Alsem, Daan Hein
Pierron, Olivier N.
Stach, Eric A.
Muhlstein, Christopher L.
Ritchie, Robert O.
Although bulk silicon is not susceptible to fatigue, micron-scale silicon is. Several mechanisms have been proposed to explain this surprising behavior although the issue remains contentious. Here we re- view published fatigue results for micron-scale thin silicon films and find that in general they display similar trends, in that lower cyclic stresses result in larger number of cycles to failure in stress-lifetime data. We further show that one of two classes of mechanisms is invariably proposed to explain the phe- nomenon. The first class attributes fatigue to a surface effect caused by subcritical (stable) cracking in the silicon-oxide layer, e.g., reaction-layer fatigue; the second class proposes that subcritical cracking in the silicon itself is the cause of fatigue in Si films. It is our contention that results to date from single and polycrystalline silicon fatigue studies provide no convincing experimental evidence to sup- port subcritical cracking in the silicon. Conversely, the reaction-layer mechanism is consistent with existing experimental results, and moreover provides a rational explanation for the marked difference between the fatigue behavior of bulk and micron-scale silicon.
2007-02-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/48
https://doi.org/10.1002/adem.200600269
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1048
2019-06-10T13:16:55Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Anomalous resonance in a nanomechanical biosensor
Gupta, Amit K.
Nair, Pradeep R.
Akin, Demir
Ladisch, Michael R.
Broyles, Steve
Alam, Muhammad A.
Bashir, Rashid
The decrease in resonant frequency of a classical cantilever provides a sensitive measure of the mass of entities attached on its surface. This elementary phenomenon has been the basis of a new class of bio-nanomechanical devices as sensing components of integrated microsystems that can perform rapid, sensitive, and selective detection of biological and biochemical entities. Based on classical analysis, there is a widespread perception that smaller sensors are more sensitive, and this notion has motivated scaling of biosensors to nanoscale dimensions. In this work, we show that the response of a nanomechanical biosensor is far more complex than previously anticipated. Indeed, in contrast to classical microscale sensors, the resonant frequencies of the nanosensor may actually decrease or increase after attachment of protein molecules. /We demonstrate theoretically and experimentally that the direction of the frequency change arises from a size-specific modification of diffusion and attachment kinetics of biomolecules on the cantilevers. this work may have broad impact on microscale and nanoscale biosensor design, especially when predicting the characteristics of bio-nanoelectromechanical sensors functionalized with biological capture molecules.
2006-09-05T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/49
https://doi.org/10.1073/pnas.0602022103
Birck and NCN Publications
Purdue University
nanocantilevers
nanotechnology
protein absorption
virus detection
oai:docs.lib.purdue.edu:nanopub-1049
2019-06-10T13:18:15Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Enhancement of thermal interface materials with carbon nanotube arrays
Xu, Jun
Fisher, Timothy
This paper describes an experimental study of thermal contact conductance enhancement enabled by carbon nanotube (CNT) arrays synthesized directly on silicon wafers using plasma-enhanced chemical vapor deposition. Testing based on the one-dimensional reference bar method occurred in a high-vacuum environment with radiation shielding, and temperature measurements were made with an infrared camera. Results from other thermal interface materials are presented, as well as combinations of these materials with CNT arrays. Dry CNT arrays produce a minimum thermal interface resistance of 19.8 mm2 K/W, while the combination of a CNT array and a phase change material produces a minimum resistance of 5.2 mm2 K/W.
2006-01-06T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/50
https://doi.org/10.1016/j.ijheatmasstransfer.2005.09.039
Birck and NCN Publications
Purdue University
Carbon nanotube array; Thermal contact conductance enhancement; Thermal interface material
oai:docs.lib.purdue.edu:nanopub-1050
2019-06-10T13:19:20Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Low-voltage ionization of air with carbon-based materials
Peterson, M S
Zhang, W
Fisher, Timothy
Garimella, Suresh
Polycrystalline diamond and carbon nanotubes (CNTs) exhibit excellent vacuum field emission properties, characterized by low turn-on voltage and high current density. Their atmospheric field emission and ionization capabilities are reported in this paper. Highly graphitic polycrystalline diamond (HGPD) film was grown in a plasma-enhanced chemical vapour deposition process, and its ability to ionize atmospheric air was characterized and compared against CNTs. The HGPD sample was activated by applying a moderate voltage bias (340 V) for an extended period across a 10μm electrode gap. After activation, a turn-on voltage of 20V and a sustainable current of 10μA were observed with the same gap. Results also indicate that field emission helps to create a moderate ionization effect without catastrophic air breakdown. A hydrogen plasma treatment is shown to restore emission current back to or even exceeding the original level, which suggests an important role of surface termination in the electron emission process. CNTs were grown and tested but did not perform as well under similar conditions.
2005-09-02T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/51
doi.org/10.1088/0963-0252/14/4/003
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1052
2019-06-10T13:21:00Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Simulation of ion generation and breakdown in atmospheric air
Zhang, W.
Fisher, Timothy
Garimella, Suresh
Understanding of ion generation in air provides insights to several applications, such as gas sensors, electrohydrodynamic pumping, and air purification. In this paper, ion generation processes in atmospheric air are simulated using a particle-in-cell and Monte Carlo method with emphasis on the prediction of ion generation and breakdown characteristics in microscale gaps. The simulation results are validated through comparison to Townsend’s discharge theory and experiments. The significance of each relevant electron-molecule reaction is characterized to improve understanding of ion generation dynamics. Self-sustaining discharge and ionization are predicted under sufficient voltage bias, and the predicted trends of breakdown voltage are similar to those obtained from Paschen’s curve. Corrections to Paschen’s curve in microscale gaps also are identified and compare well to experiments. Electron field emission produces stable electron current that suggests a controllable ionization device without external electron injection sources.
2004-12-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/53
https://doi.org/10.1063/1.1806264
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1051
2007-05-08T19:30:46Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Work function reduction of graphitic nanofibers by potassium intercalation
Robinson, V S
Fisher, Timothy
Michel, J. A.
Lukehart, C. M.
Materials with low work functions hold great potential for improving the performance of thermionic energy converters and other thermionic emission devices. Thermionic electron energy distributions !TEEDs" of graphitic carbon nanofibers !GCNFs" with and without intercalated potassium are used to characterize performance under realistic operating conditions. TEEDs of intercalated GCNFs at temperatures of 600 and 700 °C reveal an effective work function of 2.2 eV, a reduction of 2.5 eV from the work function of the GCNF without intercalate. In addition, consistent with other published work, a narrowing of the electron energy spectrum’s width occurs with intercalation. This narrower energy distribution may indicate emission from hybridized carbon–potassium states.
2005-08-03T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/52
https://docs.lib.purdue.edu/context/nanopub/article/1051/viewcontent/Fisher_013.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1053
2019-06-10T13:24:09Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Analysis and Simulation of Anode Heating Due to Electron Field Emission
Fisher, Timothy
Walker, D. G.
Weller, Robert A.
This paper considers the effect of anode heating from energetic electrons produced by field emission. Large electric fields accelerate emitted electrons as they traverse the vacuum gap toward the anode. Electron energy is transferred to the anode by collisions with the lattice. The nonequilibrium transfer of electron kinetic energy to anode thermal energy is examined quantitatively. Results demonstrate that the energy distribution of impinging electrons affects the transmission and dissipation of thermal energy. A Monte Carlo technique is used to resolve the thermalization of electrons and accounts for electron beam strength and spatial distribution. The results indicate that local heat fluxes of the order 10 occur at the anode surface and that heating is a strong function of field strength because of the exponential relationship between applied voltage and current. Under practical conditions, temperature increases of 10 degrees C are predicted from a single point emission source.
2003-06-01T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/54
https://doi.org/10.1109/TCAPT.2003.815090
Birck and NCN Publications
Purdue University
Anode heating
electron field emission
Monte Carlo
oai:docs.lib.purdue.edu:nanopub-1054
2019-06-10T13:35:01Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Freestanding vertically oriented single-walled carbon nanotubes synthesized using microwave plasma-enhanced CVD
Maschmann, Matthew R.
Amama, Placidus B
Goyal, A.
iqbal, z.
Fisher, Timothy
Freestanding single-walled carbon nanotubes (SWCNTs) have been synthesized in a vertical direction, perpendicular to the growth substrate, using applied DC substrate bias in a microwave plasma-enhanced chemical vapor deposition (PECVD) synthesis process. The degree of alignment and spatial density of SWCNTs demonstrate a strong dependence on the magnitude of applied bias, with increased alignment and decreased density with increased bias. The unique synthesis environment created by the application of a negative substrate bias in PECVD aligns SWCNTs along electric field lines and decreases SWCNT density due to bombardment by positively charged hydrogen ions. Multi-excitation wavelength Raman spectroscopy reveals shifts in dominant RBM peaks with the application of dc bias. Use of this technique to orient SWCNTs in the vertical direction may allow for three-dimensional SWCNT-based device architectures.
2006-06-06T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/55
https://doi.org/10.1016/j.carbon.2006.03.040
Birck and NCN Publications
Purdue University
Carbon nanotubes
Plasma deposition
Raman spectroscopy
oai:docs.lib.purdue.edu:nanopub-1055
2019-06-10T13:36:48Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
The Atomistic Green's Function Method: An Efficient Simulation Approach for Nanoscale Phonon Transport
Zhang, W.
Fisher, Timothy
Mingo, N.
This article presents a general formulation of an atomistic Green’s function (AGF) method. The atomistic Green’s function approach combines atomic-scale fidelity with asymptotic treatment of large-scale (bulk) features, such that the method is particularly well suited to address an emerging class of multiscale transport problems. A detailed mathematical derivation of the phonon transmission functionis provided in terms of Green’s functions and, using the transmission function, the heat flux integral is written in Landauer form. Within this theoretical framework, the required inputs t ocalculate heat flux are equilibrium atomic locations and an appropriate interatomic potential. Relevant algorithmic and implementation details are discussed. Several examples including a homogeneous atomic chain and two heterogeneous atomic chains are included to illustrate thea pplications of this methodology.
2007-04-03T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/56
https://doi.org/10.1080/10407790601144755
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1056
2019-06-24T13:36:04Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Lithography-Free in Situ Pd Contacts to Templated Single-Walled Carbon Nanotubes
Maschmann, Matthew R.
Franklin, Aaron D.
Scott, Adina
Sands, Timothy D
Fisher, Timothy
We report a metalization technique for electrically addressing templated vertical single-walled carbon nanotubes (SWNTs) using in situ palladium (Pd) nanowires. SWNTs are synthesized from an embedded catalyst in a modified porous anodic alumina (PAA) template. Pd is electrodeposited into the template to form nanowires that grow from an underlying conductive layer beneath the PAA and extend to the initiation sites of the SWNTs within each pore. In this way, individual vertical channels of SWNTs are created, each with a vertical Pd nanowire back contact. Further Pd deposition results in annular Pd nanoclusters that form on portions of SWNTs extending onto the PAA surface. Two-terminal electrical characteristics produce linear I-V relationships, indicating ohmic contact in the devices.
2006-11-09T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/61
http://doi.org/10.1021/nl061652+
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1060
2019-06-10T13:41:44Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Photoacoustic characterization of carbon nanotube array thermal interfaces
Cola, Baratunde A
Xu, Jun
Cheng, Changrui
Xu, Xianfan
Fisher, Timothy
This work describes an experimental study of thermal conductance across multiwalled carbon nanotube
2007-03-12T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/57
https://doi.org/10.1063/1.2510998
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1059
2007-05-17T17:35:14Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Increased real contact in thermal interfaces: A carbon nanotube/foil material
Cola, Baratunde A
Xu, Xianfan
Fisher, Timothy
The thermal performance of an interface material comprised of a metal foil with dense, vertically oriented carbon nanotube
2007-03-02T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/58
https://docs.lib.purdue.edu/context/nanopub/article/1059/viewcontent/Fisher_023.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1058
2019-06-10T13:40:34Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Experimental characterization of anode heating by electron emission from a multi-walled carbon nanotube
Westover, T.
Fisher, Timothy
Pfefferkorn, F.
The steady-state temperature distribution in a thin anode bombarded by an electron beam field emitted from an individual multi- walled carbon nanotube is measured with an infrared camera, and this distribution is compared to that predicted by a numerical model. By assuming the electron distribution in the beam follows a Gaussian distribution, a good fit to the anode temperature profile is obtained and this fit provides an estimate of the beam spreading radius. Results indicate the electron beam narrows as the emission current increases. A heat flux on the anode surface as high as 0.35 W/cm2 has been measured, corresponding to an electron beam radius of approximately 1.22 mm.
2006-10-02T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/59
http://dx.doi.org/10.1016/j.ijheatmasstransfer.2006.07.024
Birck and NCN Publications
Purdue University
field emission; carbon nanotube; anode heating
oai:docs.lib.purdue.edu:nanopub-1057
2019-06-10T13:37:50Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
In-place fabrication of nanowire electrode arrays for vertical nanoelectronics on Si substrates
Franklin, Aaron D.
Maschmann, Matthew R.
DaSilva, Manuel
Janes, David B.
Fisher, Timothy
Sands, Timothy D
Vertical arrays of Pd nanowire electrodes with controllable and reproducible diameters and lengths are fabricated using a porous anodic alumina
2007-03-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/60
https://doi.org/10.1116/1.2647379
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1061
2019-06-10T13:42:50Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Solid-state nanopore channels with DNA selectivity
Iqbal, Samir Muzaffar
Akin, Demir
Bashir, Rashid
Solid-state nanopores have emerged as possible candidates for next-generation DNA sequencing devices. In such a device, the DNA sequence would be determined by measuring how the forces on the DNA molecules, and also the ion currents through the nanopore, change as the molecules pass through the nanopore. Unlike their biological counterparts, solid-state nanopores have the advantage that they can withstand a wide range of analyte solutions and environments. Here we report solid-state nanopore channels that are selective towards single-stranded DNA (ssDNA). Nanopores functionalized with a ‘probe’ of hair-pin loop DNA can, under an applied electrical field, selectively transport short lengths of ‘target’ ssDNA that are complementary to the probe. Even a single base mismatch between the probe and the target results in longer translocation pulses and a significantly reduced number of translocation events. Our single-molecule measurements allow us to measure separately the molecular flux and the pulse duration, providing a tool to gain fundamental insight into the channel – molecule interactions. The results can be explained in the conceptual framework of diffusive molecular transport with particle – channel interactions.
2007-04-01T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/62
https://doi.org/10.1038/nnano.2007.78
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1062
2019-06-10T13:44:01Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Ionic winds for locally enhanced cooling
Go, David
Garimella, Suresh
Fisher, Timothy
Mongia, Rajiv K.
Ionic wind engines can be integrated onto surfaces to provide enhanced local cooling. Air ions generated by field-emitted electrons or a corona discharge are pulled by an electric field and exchange momentum with neutral air molecules, causing air flow. In the presence of a bulk flow, ionic winds distort the boundary layer, increasing heat transfer from the wall. Experiments demonstrate the ability of ionic winds to decrease the wall temperature substantially in the presence of a bulk flow over a flat plate, corresponding to local enhancement of the heat transfer coefficient by more than twofold. Multiphysics simulations of the corona and flow describe the ability of the ionic wind to distort a bulk flow boundary layer and confirm the experimentally observed heat transfer enhancement trends.
2007-09-01T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/63
https://doi.org/10.1063/1.2776164
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1064
2019-06-10T13:50:58Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Assemblies of Carbon Nanotubes and Unencapsulated Sub-10-nm Gold Nanoparticles
Hang, Qingling
Maschmann, Matthew R.
Fisher, Timothy
Janes, David B
The development ofassemblies consisting ofunencapsulated, sub-10-nm gold particles attached to individual carbon nanotubes (CNTs) with diameters of 2 nm is described. The assemblies are formed on the surface ofa porous anodic alumina (PAA) template on which the CNTs (singleor double-walled) are grown by plasma-enhanced chemical vapor deposition. The Au nanoparticles are formed through an indirect evaporation technique using a silicon nitride membrane mask, and diffuse along the PAA surface into the regions containing CNTs. The nanoparticles bind relatively strongly to the CNTs, as indicated by observations ofnanoparticles that are suspended over pores or that move along with the CNTs. This approach may provide a new method to functionalize CNTs for chemical or biological sensing and fundamental studies of nanoscale contacts to CNTs.
2007-05-08T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/65
https://doi.org/10.1002/smll.200600703
Birck and NCN Publications
Purdue University
carbon nanotubes
gold
indirect evaporation
nanoparticles
oai:docs.lib.purdue.edu:nanopub-1065
2019-06-24T13:37:55Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Controlled Decoration of Single-Walled Carbon Nanotubes with Pd Nanocubes
Franklin, Aaron
Smith, Joshua Thomas
Sands, Timothy D
Fisher, Timothy
Choi, Kyoung-Shin
Janes, David B
Although there have been many reports of nanoparticle-decorated single-walled carbon nanotubes (SWCNTs), the morphology of the resulting nanoparticles has lacked consistency and control. The present work demonstrates a process for decorating SWCNTs with Pd nanoparticles that have a tendency toward a selective and distinct cubic shape. SWCNTs were synthesized from an embedded catalyst in a porous anodic alumina (PAA) template. A single galvanostatic electrodeposition created Pd nanowires that contacted the SWCNTs within the pores and Pd nanoparticles that decorated the SWCNTs above the surface of the PAA. A distinct change in potential was observed as nanoparticles nucleated on the SWCNTs. The effects of current density and deposition time on the morphology of the nanoparticles were studied. Optimal deposition parameters yielded Pd nanocubes with smooth and flat facets. The electrochemical response and resulting nanocubic deposits provide insights into the difference in electrochemistry between metallic and semiconducting SWCNTs that are consistent with a disparity in the electron-transfer kinetics. Obtaining Pd nanoparticles of consistent shape that are electrically addressed by SWCNTs provides an improved structure for a variety of nanoparticle applications.
2007-08-24T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/66
http://doi.org/10.1021/jp074411e
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1063
2019-06-10T13:49:29Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Dendrimer-assisted controlled growth of carbon nanotubes for enhanced thermal interface conductance
Amama, Placidus B
Cola, Baratunde A
Sands, Timothy D
Xu, Xianfan
Fisher, Timothy
Multi-walled carbon nanotubes (MWCNTs) with systematically varied diameter distributions and defect densities were reproducibly grown from a modified catalyst structure templated in an amine-terminated fourth-generation poly(amidoamine) (PAMAM) dendrimer by microwave plasma-enhanced chemical vapor deposition. Thermal interface resistances of the vertically oriented MWCNT arrays as determined by a photoacoustic technique reveal a strong correlation with the quality as assessed by Raman spectroscopy. This study contributes not only to the development of an active catalyst via a wet chemical route for structure-controlled MWCNT growth, but also to the development of efficient and low-cost MWCNT-based thermal interface materials with thermal interface resistances.
2007-08-29T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/64
https://doi.org/10.1088/0957-4484/18/38/385303
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1067
2019-06-10T14:01:47Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Optimization of carbon nanotube synthesis from porous anodic Al–Fe–Al templates
Maschmann, Matthew
Franklin, Aaron D
Sands, Timothy D
Fisher, Timothy
A parametric study of carbon nanotube (CNT) synthesis from catalytically active porous anodic Al–Fe–Al multilayer templates was conducted with respect to pore aspect ratio, Fe layer thickness, CNT synthesis temperature, and pre-anodization thermal annealing. Performance metrics included CNT catalytic activity and the pore wall integrity at the Al–Fe–Al interface. The observed CNT density was a strong function of pore diameter, synthesis temperature and pre-anodization annealing of the catalyst film. Vertical pore wall integrity at the Al–Fe–Al interface was optimized by selection of pre-anodization annealing conditions, with interfacial void formation observed in the absence of this technique. Based on CNT growth rates, an activation energy of 0.52 eV was observed for CNT synthesis for all film structures, regardless of pore aspect ratio. The optimization of templated CNT synthesis is expected to assist in the development of highdensity vertically oriented CNT-based devices.
2007-06-28T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/67
https://doi.org/10.1016/j.carbon.2007.05.031
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1068
2019-06-10T14:03:14Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Synthesis and thermionic emission properties of graphitic carbon nanofibres supported on Si wafers or carbon felt
Li, Jiang
Robinson, Vance S
Liu, Yang
Lu, Weijie
Fisher, Timothy
Lukehart, Charles M
Preparation procedures and thermionic emission properties of graphitic carbon nanofibres (GCNFs) supported on Si wafer or commercial carbon felt supports are reported. GCNF/native-oxide Si wafer, GCNF/oxidized Si wafer, GCNF/Ni-coated Si wafer and GCNF/carbon felt nanocomposites are obtained by growing GCNFs from growth catalyst nanoparticles supported on these supports. Narrow herringbone GCNF/SiO2/carbon felt mats are prepared from growth catalyst nanoparticles supported on fumed silica flakes. Due to weak GCNF-to-support binding in GCNF/Si wafer mats, GCNF/carbon felt mats and GCNF/SiO2/carbon felt mats, mechanical loss of the GCNF component is facile. However, carbothermal reduction of GCNF/SiO2/carbon felt nanocomposites affords mechanically robust GCNF/SiC/carbon felt mats. Thermionic electron energy distribution profiles recorded for these new nanofibre compositions indicate classic free-electron emission with estimated work functions (4.25–4.91 eV) slightly lower than those observed for un-doped graphite or carbon nanotubes. Electron energy distributions along the low energy leading region of the profiles display a cascade of emission peaks equally spaced by ca 0.014 eV, tentatively attributed to electron emission from localized GCNF edge sites.
2007-07-13T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/72
https://doi.org/10.1088/0957-4484/18/32/325606
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1070
2019-06-10T14:05:21Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Effects of carbon nanotube arrays on nucleate pool boiling
Ujereh, Sebastine
Fisher, Timothy
Mudawar, Issam
Experiments were performed to assess the impact coating silicon and copper substrates with nanotubes (CNTs) have on pool boiling performance. Different CNT array densities and area coverages were tested on 1.27 mm2 samples in FC-72. The CNT preparation techniques used provided strong adherence of CNTs to both substrate materials. Very small contact angle enabled deep penetration of FC-72 liquid inside surface cavities of smooth uncoated silicon surfaces, requiring unusually high surface superheat to initiate boiling. Fully coating the substrate surface with CNTs was highly effective at reducing the incipience superheat and greatly enhancing both the nucleate boiling heat transfer coefficient and critical heat flux (CHF). Efforts to further improve boiling performance by manipulating CNT area coverage of the substrate surface proved ineffective; best results were consistently realized with full surface coverage. Greater enhancement was achieved on silicon than on copper since, compared to uncoated copper surfaces, the uncoated silicon surfaces were very smooth and void of any sizeable nucleation sites to start with. This study is concluded with detailed metrics to assess the enhancement potential of the different CNT array densities and area coverages tested.
2007-03-27T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/70
https://doi.org/10.1016/j.ijheatmasstransfer.2007.01.030
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1072
2019-06-24T13:43:48Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Simulation of Interfacial Phonon Transport in Si–Ge Heterostructures Using an Atomistic Green’s Function Method
Zhang, W
Fisher, Timothy
Mingo, N.
An atomistic Green’s function method is developed to simulate phonon transport across a strained germanium (or silicon) thin film between two semi-infinite silicon (or germanium) contacts. A plane-wave formulation is employed to handle the translational symmetry in directions parallel to the interfaces. The phonon transmission function and thermal conductance across the thin film are evaluated for various atomic configurations. The contributions from lattice straining and material heterogeneity are evaluated separately, and their relative magnitudes are characterized. The dependence of thermal conductance on film thickness is also calculated, verifying that the thermal conductance reaches an asymptotic value for very thick films. The thermal boundary resistance of a single Si/Ge interface is computed and agrees well with analytical model predictions. Multiple-interface effects on thermal resistance are investigated, and the results indicate that the first few interfaces have the most significant effect on the overall thermal resistance.
2007-04-30T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/73
http://doi.org/10.1115/1.2709656
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1071
2019-06-10T14:06:36Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
1 kWe sodium borohydride hydrogen generation system Part II: Reactor modeling
Zhang, Jinsong
Zheng, Yuan
Gore, Jay P
Mudawar, Issam
Fisher, Timothy
Sodium borohydride (NaBH4) hydrogen storage systems offer many advantages for hydrogen storage applications. The physical processes inside a NaBH4 packed bed reactor involve multi-component and multi-phase flow and multi-mode heat and mass transfer. These processes are also coupled with reaction kinetics. To guide reactor design and optimization, a reactor model involving all of these processes is desired. A onedimensional numerical model in conjunction with the assumption of homogeneous catalysis is developed in this study. Two submodels have been created to simulate non-isothermal water evaporation processes and pressure drop of two-phase flow through the porous medium. The diffusion coefficient of liquid inside the porous catalyst pellets and the mass transfer coefficient of water vapor are estimated by fitting experimental data at one specified condition and have been verified at other conditions. The predicted temperature profiles, fuel conversion, relative humidity and pressure drops match experimental data reasonably well.
2007-03-15T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/69
http://dx.doi.org/10.1016/j.jpowsour.2007.03.025
Birck and NCN Publications
Purdue University
Sodium borohydride; Reactor modeling; Porous media; Multi-phase
oai:docs.lib.purdue.edu:nanopub-1069
2007-10-04T12:56:14Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Correlating electrical resistance to growth conditions for multiwalled carbon nanotubes
Lan, Chun
Amama, Placidus B
Fisher, Timothy
Reifenberger, R.
A correlation between growth temperature and electrical resistance of multiwalled carbon nanotubes MWNTs has been established by measuring the resistance of individual MWNTs grown by microwave plasma-enhanced chemical vapor deposition PECVD at 800, 900, and 950 °C. The lowest resistances were obtained mainly from MWNTs grown at 900 °C. The MWNT resistance is larger on average at lower 800 °C and higher 950 °C growth temperatures. The resistance of MWNTs correlated well with other MWNT quality indices obtained from Raman spectra. This study identifies a temperature window for growing higher-quality MWNTs with fewer defects and lower resistance by PECVD.
2007-08-28T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/71
https://docs.lib.purdue.edu/context/nanopub/article/1069/viewcontent/Lan_MWCNT_resistance_APL_07.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1075
2019-06-24T13:47:23Z
publication:dp
publication:engr
publication:chempubs
publication:chem
publication:nano
publication:nanopub
publication:ece
publication:sci
publication:ecepubs
Resonant Field Enhancements from Metal Nanoparticle Arrays
Genov, Dentcho A.
Sarychev, Andrey K.
Shalaev, Vladimir M.
Wei, Alexander
Theoretical and semiempirical studies of two-dimensional (2D) metal nanoparticle arrays under periodic boundary conditions yield quantitative estimates of their electromagnetic (EM) field factors, revealing a critical relationship between particle size and interparticle spacing. A new theory based on the RLC circuit analogy has been developed to produce analytical values for EM field enhancements within the arrays. Numerical and analytical calculations suggest that the average EM enhancements for Raman scattering can approach 2x10^11 for Ag nanodisks (5x10^10 for Au) and 2x10^9 for Ag nanosphere arrays (5x10^8 for Au). Radiative losses related to retardation or damping effects are less critical to the EM field enhancements from periodic arrays compared to that from other nanostructured metal substrates. These findings suggest a straightforward approach for engineering nanostructured arrays with direct application toward surface-enhanced Raman scattering (SERS).
2004-01-15T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/75
http://doi.org/10.1021/nl0343710
Birck and NCN Publications
Purdue University
electromagnetic theory
SERS
2D arrays
oai:docs.lib.purdue.edu:nanopub-1074
2019-06-24T13:46:22Z
publication:dp
publication:engr
publication:chempubs
publication:chem
publication:nano
publication:nanopub
publication:ece
publication:sci
publication:ecepubs
Dithiocarbamate Assembly on Gold
Zhao, Yan
Perez-Segarra, Waleska
Shi, Qicun
Wei, Alexander
Metal surfaces are functionalized by stable dithiocarbamate ligands when exposed to carbon disulfide and secondary amines. The adsorbed dithiocarbamates are robust under a wide pH range and can resist displacement by other chemisorptive surfactants, providing an attractive method for conjugating sensitive molecules onto metal surfaces.
2005-05-23T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/76
http://doi.org/10.1021/ja050432f
Birck and NCN Publications
Purdue University
surface chemistry
self-assembled monolayers
SERS
oai:docs.lib.purdue.edu:nanopub-1073
2019-06-24T13:44:51Z
publication:dp
publication:engr
publication:chempubs
publication:chem
publication:nano
publication:nanopub
publication:ece
publication:sci
publication:ecepubs
Uniform Gold Nanorod Arrays from Polyethylenimine-coated Alumina Templates
Moon, Jeong-mi
Wei, Alexander
Monolithic Au nanorod arrays can be grown by electrodeposition in Au-backed nanoporous alumina templates using polyethylenimine (PEI) as an adhesion layer, with excellent height control between 300 nm and 1.4 microns. The local height distribution can be extremely narrow with relative standard deviations well below 2%. The uniform growth rate appears to be determined by the adsorbed PEI matrix, which controls the growth kinetics of the grains comprising the nanorods. The nanorods can be retained as free-standing 2D arrays after careful removal of the AAO template. Reflectance spectroscopy reveals a collective plasmon mode with a maximum near 1.2 μm, in accord with recent calculations for 2D arrays of closely spaced cylindrical nanoparticles.
2005-11-17T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/77
http://doi.org/10.1021/jp054405n
Birck and NCN Publications
Purdue University
nanorods
porous
electrochemistry
oai:docs.lib.purdue.edu:nanopub-1076
2019-06-10T14:07:47Z
publication:dp
publication:engr
publication:chempubs
publication:chem
publication:nano
publication:nanopub
publication:ece
publication:sci
publication:ecepubs
Flux Closure in Self-Assembled Cobalt Nanoparticle Rings
Tripp, Steven L.
Dunin-Borkowski, Rafal E.
Wei, Alexander
Chiral magnetic domains are observed when ferromagnetic Co nanoparticles self-assemble into bracelet-like rings. The magnetic dipoles of the particles collectively contribute toward flux closure, a bistable state with potential utility for nonvolatile data storage.
2003-11-03T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/74
https://doi.org/10.1002/anie.200352825
Birck and NCN Publications
Purdue University
magnetic nanoparticles
flux closure
electron microscopy
oai:docs.lib.purdue.edu:nanopub-1077
2008-02-21T14:08:33Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Independently addressable fields of porous anodic alumina embedded in SiO2 on Si
Franklin, Aaron D
Janes, David B
Claussen, Jonathan
Fisher, Timothy
Sands, Timothy D
Fields of thin-film porous anodic alumina PAA are fabricated within a SiO2 support and on independently addressable underlying metal pads. The underlying metallization provides a means for unique postprocessing to be performed on the PAA fields. Customized postprocessing is demonstrated with the synthesis of single-walled carbon nanotubes SWCNTs from an embedded catalyst in the PAA, followed by selective decoration of the SWCNTs from different PAA fields with dissimilar nanoparticles. Achieving uniquely functionalized fields of PAA on a single chip provides a scalable integration platform to be used in multiplexed chemical and biological sensing or nanoelectronic devices. © 2008 American Institute of Physics. DOI: 10.1063/1.2831002
2008-01-08T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/78
https://docs.lib.purdue.edu/context/nanopub/article/1077/viewcontent/Franklin_CNT_PAA_fields_APL_08.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1080
2019-06-10T14:11:18Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Recent advances in microscale pumping technologies: a review and evaluation
Iverson, Brian D.
Garimella, Suresh
Micropumping has emerged as a critical research area for many electronics and biological applications. A significant driving force underlying this research has been the integration of pumping mechanisms in micro total analysis systems and other multi-functional analysis techniques. Uses in electronics packaging and micromixing and microdosing systems have also capitalized on novel pumping concepts. The present work builds upon a number of existing reviews of micropumping strategies by focusing on the large body of micropump advances reported in the very recent literature. Critical selection criteria are included for pumps and valves to aid in determining the pumping mechanism that is most appropriate for a given application. Important limitations or incompatibilities are also addressed. Quantitative comparisons are provided in graphical and tabular forms.
2008-01-31T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/81
https://doi.org/10.1007/s10404-008-0266-8
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1082
2019-06-10T14:12:46Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Measurement of metal/carbon nanotube contact resistance by adjusting contact length using laser ablation
Lan, Chun
Srisungsitthisunti, Pornsak
Amama, Placidus B
Fisher, Timothy
Xu, Xianfan
Reifenberger, R.
A technique of measuring contact resistance between an individual nanotube and a deposited metallic film is described. Using laser ablation to sequentially shorten the contact length between a nanotube and the evaporated metallic film, the linear resistivity of the nanotube as well as the specific contact resistivity between the nanotube and metallic film can be determined. This technique can be generally used to measure the specific contact resistance that develops between a metallic film and a variety of different nanowires and nanotubes.
2008-03-03T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/98
https://doi.org/10.1088/0957-4484/19/12/125703
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1084
2019-06-24T13:48:25Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Microscale pumping technologies for microchannel cooling systems
Singhal, Vishal
Garimella, Suresh
Raman, Arvind
A review of the state of the art in micropumping technologies for driving fluid through microchannels is presented with a particular emphasis on small-scale cooling applications. An extensive variety of micropumping techniques developed over the past fifteen years in the literature is reviewed. The physical principles, engineering limitations, and advantages of approximately twenty different kinds of micropumps are reviewed. The available micropumping techniques are compared quantitatively, primarily in terms of the maximum achievable flow rate per unit cross-sectional area of the microchannel and the maximum achievable back pressure. A concise table is developed to facilitate the convenient comparison of the micropumps based on different criteria including their miniaturization potential, size ~in-plane and out-of-plane!, actuation voltage and power required per unit flow rate, ease and cost of fabrication, minimum and maximum frequency of operation, and suitability for electronics cooling. Some important performance characteristics of the micropumps, which are likely to be decisive for specific applications, are also discussed. The current state of the art in micropump design and fabrication is also comprehensively reviewed. There are 171 references cited in this review article. @DOI: 10.1115/1.1695401#
2004-05-01T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/84
https://doi.org/10.1115/1.1695401
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1085
2008-03-05T20:23:29Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Nanopatterning using NSOM probes integrated with high transmission nanoscale bowtie aperture
Murphy-DuBay, Nicholas
Wang, Liang
Kinzel, Edward C
Uppuluri, Sreemanth M. V.
Xu, Xianfan
Nanoscale ridge aperture antennas have been shown to have high transmission efficiency and confined nanoscale radiation in the near field region compared with regularly-shaped apertures. The radiation enhancement is attributed to the fundamental electric-magnetic field propagating in the TE10 mode concentrated in the gap between the ridges. This paper reports experimental demonstration of field enhancement using such ridge antenna apertures in a bowtie shape for the manufacture of nanometer size structures using an NSOM (near field scanning optical microscopy) probe integrated with nanoscale bowtie aperture. Consistent lines with width of 59 nm and as small as 24 nm have be written on photoresist using such probes.
2008-02-11T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/85
https://docs.lib.purdue.edu/context/nanopub/article/1085/viewcontent/2008.02.Nick_20OE.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1086
2019-06-10T14:14:02Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Effects of discrete-electrode configuration on traveling-wave electrohydrodynamic pumping
Iverson, Brian D.
Cremaschi, Lorenzo
Garimella, Suresh
Traveling-wave electrohydrodynamic (EHD) micropumps can be incorporated into the package of an integrated circuit chip to provide active cooling. They can also be used for fluid delivery in microdevices. The pump operates in the presence of a thermal gradient through the fluid layer such that a gradient in electrical conductivity is established allowing ions to be induced. These ions are driven by a traveling electric field. Such a traveling electric field can be realized in practice only via discrete electrodes upon which the required voltages are imposed. The impact of using discrete electrodes to create the traveling wave on the flow rates generated is explored through numerical modeling. The change in performance from an ideal sinusoidal voltage boundary condition is quantified. The model is used to explore the widths of electrodes and the intervening isolation regions that lead to optimized pumping. The influence of the choice of working fluid on the performance of the pump is determined using an analytical model.
2009-01-01T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/86
https://doi.org/10.1007/s10404-008-0317-1
Birck and NCN Publications
Purdue University
Nanoscience and Nanotechnology
oai:docs.lib.purdue.edu:nanopub-1087
2008-07-29T22:38:45Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Highly ordered diamond and hybrid triangle-diamond patterns in porous anodic alumina thin films
Smith, Joshua T
Hang, Qingling
Franklin, Aaron D
Janes, David B
Sands, Timothy D
Utilizing nonequilibrium formation kinetics in porous anodic alumina (PAA) thin films, diamond and hybrid triangle-diamond pore patterns are achieved. During anodization, the self-compensation abilities of PAA allow diamond-shaped pores to form by omitting certain sites in the surface prepatterning process. The effects of tessellation on cell formation in these arrangements yield elongated, regular, and partially compressed hexagonal cell structures leading to diamond, circular, and triangular pores, respectively. The diamond-shaped porous templates provide a low-cost option for the preparation of scalable nanostructures with diamond-shaped cross sections with utility in a range of nanoscale applications, including enhanced sensing and field emission. © 2008 American Institute of Physics. [DOI: 10.1063/1.2957991]
2008-07-29T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/97
https://docs.lib.purdue.edu/context/nanopub/article/1087/viewcontent/Highly_ordered_diamond_and_hybrid_triangle_diamond_patterns_in_PAA___APL__2008____Smith.pdf
Birck and NCN Publications
Purdue University
template
porous
anodic
alumina
diamond-shaped
diamond
triangle
oai:docs.lib.purdue.edu:nanopub-1088
2019-06-10T14:15:20Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
XPS and Raman characterization of single-walled carbon nanotubes grown from pretreated Fe2O3 nanoparticles
Amama, Placidus B
Zemlyanov, Dmitry
Sundarakannan, B
Katiyar, Ram S
Fisher, Timothy
X-ray photoelectron (XPS) and Raman spectroscopic techniques have been used to study the influence of the annealing ambient (N2, Ar and H2) of nearly monodispersed Fe2O3 nanoparticles (mean size = 3.2 ± 1 nm) on the growth of carbon nanotubes by microwave plasma chemical vapour deposition. XPS characterization of the catalytic templates reveals that a N2 ambient reduces sintering of the Fe2O3 nanoparticles and confirms that the chemical phase involved in the nucleation of nanotubes is the metal state Fe0. Multi-excitation wavelength Raman spectroscopy (514, 574, 633 and 785 nm) reveals that the single-walled carbon nanotubes (SWCNTs) grown from N2-annealed catalyst nanoparticles range between 0.8 and 1.1 nm while SWCNTs grown from Ar-annealed catalyst nanoparticles exhibit a broader diameter distribution in the range 0.8–1.8 nm. The narrowness in the distribution of SWCNTs grown from the N2-annealed catalysts has been attributed to the enhanced stability of Fe2O3 nanoparticles in an N2 ambient.
2008-07-31T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/87
https://doi.org/10.1088/0022-3727/41/16/165306
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1092
2019-06-24T13:50:49Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Effects of Feed Gas Composition and Catalyst Thickness on Carbon Nanotube and Nanofiber Synthesis by Plasma Enhanced Chemical Vapor Deposition
Garg, R K
Kim, S S
Hash, D. B
Gore, Jay P.
Fisher, Timothy
Many engineering applications require carbon nanotubes with specific characteristics such as wall structure, chirality and alignment. However, precise control of nanotube properties grown to application specifications remains a significant challenge. Plasma-enhanced chemical vapor deposition (PECVD) offers a variety of advantages in the synthesis of carbon nanotubes in that several important synthesis parameters can be controlled independently. This paper reports an experimental study of the effects of reacting gas composition (percentage methane in hydrogen) and catalyst film thickness on carbon nanotube (CNT) growth and a computational study of gas-phase composition for the inlet conditions of experimentally observed carbon nanotube growth using different chemical reaction mechanisms. The simulations seek to explain the observed effects of reacting gas composition and to identify the precursors for CNT formation. The experimental results indicate that gas-phase composition significantly affects the synthesized material, which is shown to be randomly aligned nanotube and nanofiber mats for relatively methane-rich inlet gas mixtures and non-tubular carbon for methane-lean incoming mixtures. The simulation results suggest that inlet methane-hydrogen mixture coverts to an acetylene-methane-hydrogen mixture with minor amounts of ethylene, hydrogen atom, and methyl radical. Acetylene appears to be the indicator species for solid carbon formation. The simulations also show that inlet methane-hydrogen mixture does not produce enough gas-phase precursors needed to form quality CNTs below 5% CH4 concentrations in the inlet stream.
2008-08-01T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/91
https://doi.org/10.1166/jnn.2008.082
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1089
2019-06-10T14:19:21Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Electrothermal Bonding of Carbon Nanotubes to Glass
Aradhya, Sriharsha V
Garimella, Suresh
Fisher, Timothy
Applications that exploit the exceptional properties of carbon nanotubes CNTs[1] at practical length scales almost invariably involve the fundamental issues of nanotube-to-surface contacts; indeed, interface properties often dominate mechanical, electrical, and thermal performance in devices and materials based on CNTs. In this paper we present a method to attach CNTs to glass surfaces and investigate the mechanism of bonding at the interface. An electric field which induces migration of alkali ions from glass into CNTs, with a reversed polarity as compared to an analogous anodic bonding configuration, is employed to form a chemical bond between nanotubes and glass. We report a pull-off force of 4.35 N/cm2 averaged over the bonded area, with the possibility of localized areas of higher bonding strength.
2008-07-22T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/88
https://doi.org/10.1149/1.2952814
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1090
2019-06-10T14:20:33Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Influence of Bias-Enhanced Nucleation on Thermal Conductance Through Chemical Vapor Deposited Diamond Films
Cola, Baratunde A
Karru, Ratnakar
Cheng, Changrui
Xu, Xianfan
Fisher, Timothy
This work describes an experimental study of the cross-plane thermal conductance of plasma-enhanced chemical vapor deposited (PECVD) diamond films grown as a result of bias-enhanced nucleation (BEN). The diamond films are grown on silicon wafers using a two-step process in which a nucleation layer of amorphous or diamond like (DLC) carbon is first deposited on the silicon under the influence of a voltage bias. Then, conditions are adjusted to allow for polycrystalline diamond (PD) growth. The nucleation layer is essential for seeding diamond growth on smooth substrates and for optimizing PD properties such as grain size, orientation, transparency, adhesion, and roughness. A photoacoustic (PA) technique is employed to measure the thermal conductivities of and the thermal interface resistances between the layers in the diamond film structure. The influence of nucleation layers that are 70, 240, 400, and 650 nm thick on the thermal conductance of the diamond film structure is characterized. The thermal conductivity of the nucleation layer exhibits a thickness dependence for relatively thin layers. For each sample, the thermal conductivity of the PD is higher than 500 W m 1K 1 (measurement sensitivity limit). A resistive network for the diamond film structure is developed. The resistance at the silicon/nucleation interface is less than 10 9m2 K W 1 (measurement sensitivity limit), which is of the order of theoretical predictions. The minimum diamond film structure resistance occurs when the nucleation layer is thinnest. When the nucleation layer is sufficiently thick, it begins to exhibit bulk behavior, and the resistance at the nucleation/PD interface dominates the thermal resistance of the diamond film structure.
2008-09-08T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/89
https://doi.org/10.1109/ITHERM.2006.1645387
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1091
2019-06-24T13:49:48Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Effects of Growth Temperature on Carbon Nanotube Array Thermal Interfaces
Cola, Baratunde A
Amama, Placidus B
Xu, Xianfan
Fisher, Timothy
Due to their excellent compliance and high thermal conductivity, dry carbon nanotube (CNT) array interfaces are promising candidates to address the thermal management needs of power dense microelectronic components and devices. However, typical CNT growth temperatures 800°C limit the substrates available for direct CNT synthesis. A microwave plasma chemical vapor deposition and a shielded growth technique were used to synthesize CNT arrays at various temperatures on silicon wafers. Measured growth surface temperatures ranged from 500°C to 800°C. The room-temperature thermal resistances of interfaces created by placing the CNT covered wafers in contact with silver foil (silicon-CNT-silver) were measured using a photoacoustic technique to range from approximately 7 mm2°C/W to 19 mm2°C/W at moderate pressures. Thermal resistances increased as CNT array growth temperature decreased primarily due to a reduction in the average diameter of CNTs in the arrays.
2008-09-08T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/90
https://doi.org/10.1115/1.2969758
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1096
2019-06-10T14:24:29Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Experimental Study of Energy Exchange Attending Electron Emission from Carbon Nanotubes
Westover, Tyler
Fisher, Timothy
Phenomena based on nanoscale transport processes offer new possibilities for direct refrigeration by electron emission between opposing electrodes across a vacuum region. The average energy of emitted electrons depends upon the magnitude and shape of the potential energy barrier in the vacuum region, which is affected by the emission gap, emitter work function (potential barrier height), and emitter tip geometry. Emitted electrons are replaced by other electrons to maintain charge continuity, and the difference in energy between the emitted and replacement electrons produces a heating or cooling effect, known as the Nottingham effect, at the emitter surface. Theoretical studies indicate the possibility of very large (>100 W/cm2) cooling rates, but experimental confirmation is lacking due to challenging material and experimental requirements. To obtain the results discussed in this paper, the energy exchange attending electron emission from multi-walled carbon nanotube (MWNT) array samples is measured with an uncertainty of approximately 1 μW. The results are found to depend strongly on the adhesive used to bind the MWNT arrays to the substrate, and this effect is explored by using both silver and carbon paints as the adhesive material. An attempt to determine the effect of the emitter work function by intercalating the MWNT arrays with potassium was unsuccessful. Heating curves as a function of the emission current are presented for various sample groups, and these curves provide insight into the mechanisms involved in the energy exchange associated with field emission from MWNT arrays, including the Nottingham effect and Joule heating.
2008-02-21T08:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/95
https://doi.org/10.1080/01457630701825754
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1094
2019-06-24T13:52:34Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Synthesis and Characterization of Potassium Metal/Graphitic Carbon Nanofiber Intercalates
Michel, Jason A
Robinson, Vance S
Yang, Liu
Sambandam, Senthil
Lu, Weijie
Westover, Tyler
Fisher, Timothy
Lukehart, Charles M
Direct reaction of herringbone, platelet, or narrow, tubular herringbone graphitic carbon nanofibers (GCNFs) with molten potassium gives K/GCNF intercalates with stoichiometric control of potassium loading.Intercalate formation is confirmed by powder X-ray diffraction and micro-Raman spectroscopy. K/GCNF intercalates act as radical-anion alkene polymerization catalysts and reduce water with stoichiometric formation of hydrogen gas.Stage-1 K/narrow, tubular GCNF intercalate exhibits thermionic emission at 300 C.Stage-1 K/herringbone GCNF intercalate is an excellent thermionic emitter having high thermal stability up to 1000 C.K/GCNF intercalates have much reduced work functions of ca. 2.2 eV with localized emission showing a work function of 1.6 eV.
2008-09-03T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/93
https://doi.org/10.1166/jnn.2008.308
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1095
2019-06-24T13:54:02Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Extraordinary Sensitivity of the Electronic Structure and Properties of Single-Walled Carbon Nanotubes to Molecular Charge-Transfer
Voggu, Rakesh
Rout, Chandra S
Franklin, Aaron D
Fisher, Timothy
Rao, C. N. R.
Interaction of single-walled carbon nanotubes with electron-donor and -acceptor molecules causes significant changes in the electronic and Raman spectra. Electron-donating molecules such as tetrathiafulvalene and aniline cause changes opposite to those caused by electron-withdrawing molecules such as nitrobenzene and tetracyanoethylene. Thus, a proportion of the semiconducting SWNTs becomes metallic on electron donation through molecular charge transfer. Electrical resistivity measurements reveal a systematic variation with electron-donating or -withdrawing power of the interacting molecules.
2008-08-05T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/94
https://doi.org/10.1021/jp805136e
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1097
2019-06-10T14:26:17Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Noise analysis and sensitivity enhancement in immunomagnetic nanomechanical biosensors
Icoz, Kutay
Iverson, Brian D
Savran, Cagri
We report noise and detection limitations in cantilever-based immunomagnetic biosensors. A differential cantilever system with sensing and control arms was used whereby the control arm was passivated with bovine serum albumin BSA and the sensing arm was functionalized with biotin-BSA. Streptavidin-coated magnetic beads were exposed to cantilever arms. An oscillatory magnetic field induced a magnetic force on the beads which caused a relative deflection of the sensing arm. Increasing the excitation frequency suppressed the 1/ f noise by 100-fold, resulting in a deflection resolution of 0.065 Å in air.
2008-09-11T07:00:00Z
text
application/pdf
https://docs.lib.purdue.edu/nanopub/99
https://doi.org/10.1063/1.2980036
Birck and NCN Publications
Purdue University
biosensor
sensitivity
cantilever
magnetic
thermomechanical
oai:docs.lib.purdue.edu:nanopub-1100
2019-06-10T14:35:16Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Effect of post-release sidewall morphology on the fracture and fatigue properties of polycrystalline silicon structural films
Alsem, D H
Boyce, B L
Stach, E A
Ritchie, R O
Surface properties can markedly affect the mechanical behavior of structural thin films used in microelectromechanical systems (MEMS) applications. This study highlights the striking difference in the sidewall surface morphology of n+-type polysilicon films from two popular MEMS processes and its effect on fracture and fatigue properties. The sidewall surface roughnesswas measured using atomic force microscopy, whereas silicon oxide thickness and grain size were measured using (energy-filtered) transmission electron microscopy. These measurements show that the oxide layers are not always thin native oxides, as often assumed; moreover, the roughness of the silicon/silicon oxide interface is significantly influenced by the oxidation mechanism. Thick silicon oxides (20±5 nm) found in PolyMUMPsTM films are caused by galvanic corrosion from the presence of gold on the chip, whereas in SUMMiT VTM films a much thinner (3.5±1.0 nm) native oxidewas observed. The thicker oxide layers, in combination with differences in sidewall roughness (14±5 nmfor PolyMUMPsTM and 10±2 nmfor SUMMiT VTM), can have a significant effect on the reliability of polysilicon structures subjecting to bending loads; this is shown by measurements of the fracture strength (3.8±0.3 GPa for PolyMUMPsTM and 4.8±0.2 GPa for SUMMiT VTM) and differences in the stress-lifetime cyclic fatigue behavior.
2008-10-03T07:00:00Z
text
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https://docs.lib.purdue.edu/nanopub/107
https://doi.org/10.1016/j.sna.2008.05.027
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1099
2019-06-10T14:33:22Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
A theoretical model for single-molecule incoherent scanning tunneling spectroscopy
Raza, H
Single-molecule scanning tunneling spectroscopy (STS), with dephasing due to elastic and inelastic scattering, is of some current interest. Motivated by this, we report an extended Huckel theory (EHT)-based mean-field non-equilibrium Green's function (NEGF) transport model with electron-phonon scattering treated within the self-consistent Born approximation (SCBA). Furthermore, a procedure based on EHT basis set modification is described. We use this model to study the effect of the temperature-dependent dephasing due to low lying modes in the far-infrared range for which (h) over bar omega k(B)T, on the resonant conduction through the highest occupied molecular orbital (HOMO) level of a phenyl dithiol molecule bonded to fcc-Au(111) contact. We finally propose to include dephasing in room temperature molecular resonant conduction calculations.
2008-11-18T08:00:00Z
text
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https://docs.lib.purdue.edu/nanopub/108
https://doi.org/10.1088/0953-8984/20/44/445004
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1102
2008-11-18T15:49:04Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Graphene segregated on Ni surfaces and transferred to insulators
Yu, Qingkai
Lian, Jie
Siriponglert, Sujitra
Li, Hao
Chen, Yong P
Pei, Shin-Shem
We report an approach to synthesize high quality graphene by surface segregation and substrate transfer. Graphene was segregated from Ni surface under the ambient pressure by dissolving carbon in Ni at high temperatures followed by cooling down with various rates. Different cooling rates led to different segregation behaviors, strongly affecting the thickness and quality of the graphene films. Electron microscopy and Raman spectroscopy indicated that the graphene films synthesized with medium cooling rates have high quality crystalline structure and well-controlled thicknesses. The graphene films were transferred to insulating substrates by wet etching and found to maintain their high quality. (C) 2008 American Institute of Physics.
2008-09-15T07:00:00Z
text
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https://docs.lib.purdue.edu/nanopub/105
https://docs.lib.purdue.edu/context/nanopub/article/1102/viewcontent/ApplPhysLett_93_113103.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1107
2008-11-18T17:25:53Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Theory of the broadening of vibrational spectra induced by lowered symmetry in yttria nanostructures
Bao, H
Ruan, X
Kaviany, M
We calculate the vibrational spectra for typical nanostructures including thin films, nanowires, and quantum dots of yttria, an important laser host material. Lattice dynamics calculations show that the vibrational spectra of nanocrystals are distinct from that of the bulk phase in the enhanced tails at low and high frequencies. Some of the low-frequency and high-frequency modes only involve surface atoms. Molecular-dynamics simulations are used to further decompose the contributions of surface and internal atoms, and the results confirm the evident broadening of the surface spectra. The broadening in vibrational spectra is attributed to the broadened atomic spring constants, further to the lowered symmetry of nanostructures.
2008-09-01T07:00:00Z
text
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https://docs.lib.purdue.edu/nanopub/100
https://docs.lib.purdue.edu/context/nanopub/article/1107/viewcontent/PhysRevB_78_125417.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1106
2019-06-10T14:36:35Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Transforming light
Shalaev, V. M.
Recent advances in micro- and nanofabrication methods are presenting opportunities to control light in a way that is not possible with the materials provided to us by nature. Synthetic structures built up from subwavelength elements can now be fabricated with a desired spatial distribution of effective electric permittivity ε and magnetic permeability μ, thereby offering the potential to guide and control the flow of electromagnetic energy in an engineered optical space. These “metamaterials” have opened the door to a number of applications that had been previously considered impossible. No longer are we constrained by the electromagnetic response of natural materials and their chemical compounds. Instead, we can tailor the shape and size of the structural unit of the metamaterial and tune their composition and morphology to provide new functionality.
2008-10-17T07:00:00Z
text
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https://docs.lib.purdue.edu/nanopub/101
https://doi.org/10.1126/science.1166079
Birck and NCN Publications
Purdue University
MAXWELLS EQUATIONS
OPTICAL HYPERLENS
DIFFRACTION
CLOAKING
FORM
oai:docs.lib.purdue.edu:nanopub-1101
2008-11-18T15:25:50Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Valley splitting in Si quantum dots embedded in SiGe
Srinivasan, S
Klimeck, Gerhard
Rokhinson, Leonid P
We examine energy spectra of Si quantum dots embedded in Si0.75Ge0.25 buffers using atomistic numerical calculations for dimensions relevant to qubit implementations. The valley degeneracy of the lowest orbital state is lifted and valley splitting fluctuates with monolayer frequency as a function of the dot thickness. For dot thicknesses <= 6 nm, valley splitting is found to be > 150 mu eV. Using the unique advantage of atomistic calculations, we analyze the effect of buffer disorder on valley splitting. Disorder in the buffer leads to the suppression of valley splitting by a factor of 2.5; the splitting fluctuates with approximate to 20 mu eV for different disorder realizations. Through these simulations we can guide future experiments into regions of low device-to-device fluctuations. (C) 2008 American Institute of Physics.
2008-09-15T07:00:00Z
text
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https://docs.lib.purdue.edu/nanopub/106
https://docs.lib.purdue.edu/context/nanopub/article/1101/viewcontent/ApplPhysLett_93_112102.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1103
2008-11-18T17:03:23Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Reduction in coherent phonon lifetime in Bi2Te3/Sb2Te3 superlattices
Wang, Yaguo
Xu, Xianfan
Venkatasubramanian, Rama
Femtosecond pulses are used to excite A(1g) optical phonons in Bi2Te3, Sb2Te3, and Bi2Te3/Sb2Te3 superlattice. Time-resolved reflectivity measurements show both the low-frequency and high-frequency components of A(1g) phonon modes. By comparing the phonon lifetime, it is found that the scattering rate (inverse of lifetime) in superlattice is significantly higher than those in Bi2Te3 and Sb2Te3. This represents the direct measurement of coherent phonon lifetime reduction in superlattice structures, consistent with the observed reduction in thermal conductivity in superlattices. (c) 2008 American Institute of Physics.
2008-09-15T07:00:00Z
text
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https://docs.lib.purdue.edu/nanopub/104
https://docs.lib.purdue.edu/context/nanopub/article/1103/viewcontent/ApplPhysLett_93_113114.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1108
2019-06-10T14:37:53Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Nuclear-induced time evolution of entanglement of two-electron spins in anisotropically coupled quantum dot
Sadiek, Gehad
Huang, Zhen
Aldossary, Omar
Kais, Sabre
We study the time evolution of entanglement of two spins in an anisotropically coupled quantum dot interacting with the unpolarised nuclear spins environment. We assume that the exchange coupling strength in the z direction J(z) is different from the lateral one J(t). We observe that the entanglement decays as a result of the coupling to the nuclear environment and reaches a saturation value, which depends on the value of the exchange interaction difference J = parallel to J(t) - J(z)parallel to between the two spins and the strength of the applied external magnetic field. We find that the entanglement exhibits a critical behaviour controlled by the competition between the exchange interaction J and the external magnetic field. The entanglement shows a quasi-symmetric behaviour above and below a critical value of the exchange interaction. It becomes more symmetric as the external magnetic field increases. The entanglement reaches a large saturation value, close to unity, when the exchange interaction is far above or below its critical value and a small one as it closely approaches the critical value. Furthermore, we find that the decay rate profile of entanglement is linear when the exchange interaction is much higher or lower than the critical value but converts to a power law and finally to a Gaussian as the critical value is approached from both directions. The dynamics of entanglement is found to be independent of the exchange interaction for an isotropically coupled quantum dot.
2008-07-01T07:00:00Z
text
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https://docs.lib.purdue.edu/nanopub/110
https://doi.org/10.1080/00268970802290313
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1109
2019-06-10T14:43:46Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Electrical actuation of electrically conducting and insulating droplets using ac and dc voltages
Kumari, Niru
Bahadur, Vaibhav
Garimella, Suresh
Electrical actuation of liquid droplets at the microscale offers promising applications in the fields of microfluidics and lab-on-chip devices. Much prior research has targeted the electrical actuation of electrically conducting liquid droplets using dc voltages (classical electrowetting). Electrical actuation of conducting droplets using ac voltages and the actuation of insulating droplets (using dc or ac voltages) has remained relatively unexplored. This paper utilizes an energy-minimization-based analytical framework to study the electrical actuation of a liquid droplet (electrically conducting or insulating) under ac actuation. It is shown that the electromechanical regimes of classical electrowetting, electrowetting under ac actuation and insulating droplet actuation can be extracted from the generic electromechanical actuation framework, depending on the electrical properties of the droplet, the underlying dielectric layer and the frequency of the actuation voltage. This paper also presents experiments which quantify the influence of the ac frequency and the electrical properties of the droplet on its velocity under electrical actuation. The velocities of droplets moving between two parallel plates under ac actuation are experimentally measured; these velocities are then related to the actuation force on the droplet which is predicted by the electromechanical model developed in this work. It is seen that the droplet velocities are strongly dependent on the frequency of the ac actuation voltage; the cut-off ac frequency, above which the droplet fails to actuate, is experimentally determined and related to the electrical conductivity of the liquid. This paper then analyzes and directly compares the various electromechanical regimes for the actuation of droplets in microfluidic applications.
2008-10-01T07:00:00Z
text
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https://docs.lib.purdue.edu/nanopub/109
https://doi.org/10.1088/0960-1317/18/10/105015
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1105
2008-11-18T17:13:38Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Localized heating and thermal characterization of high electrical resistivity silicon-on-insulator sensors using nematic liquid crystals
Elibol, Oguz H
Reddy, Bobby, Jr.
Bashir, Rashid
We present a method for localized heating of media at the surface of silicon-on-insulator field-effect sensors via application of an ac voltage across the channel and the substrate and compare this technique with standard Joule heating via the application of dc voltage across the source and drain. Using liquid crystals as the medium to enable direct temperature characterization, our results show that under comparable bias conditions, heating of the medium using an alternating field results in a greater increase in temperature with a higher spatial resolution. These features are very attractive as devices are scaled to the nanoscale dimensions. (C) 2008 American Institute of Physics.
2008-09-29T07:00:00Z
text
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https://docs.lib.purdue.edu/nanopub/102
https://docs.lib.purdue.edu/context/nanopub/article/1105/viewcontent/ApplPhysLett_93_131908.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1104
2008-11-18T17:08:47Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
Magnetoconductance oscillations in graphene antidot arrays
Shen, T
Wu, Y Q
Rokhinson, Leonid P
Engel, L W
Ye, P. D.
Epitaxial graphene films have been formed on the C-face of semi-insulating 4H-SiC substrates by a high temperature sublimation process. Nanoscale square antidot arrays have been fabricated on these graphene films. At low temperatures, magnetoconductance in these films exhibits pronounced Aharonov-Bohm oscillations with the period corresponding to magnetic flux quanta added to the area of a single antidot. At low fields, weak localization is observed and its visibility is enhanced by intervalley scattering on antidot edges. At high fields, we observe two distinctive minima in magnetoconductance, which can be attributed to commensurability oscillations between classical cyclotron orbits and antidot array. All mesoscopic features, surviving up to 70 K, reveal the unique electronic properties of graphene. (C) 2008 American Institute of Physics.
2008-09-22T07:00:00Z
text
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https://docs.lib.purdue.edu/nanopub/103
https://docs.lib.purdue.edu/context/nanopub/article/1104/viewcontent/ApplPhysLett_93_122102.pdf
Birck and NCN Publications
Purdue University
oai:docs.lib.purdue.edu:nanopub-1110
2019-06-10T14:53:03Z
publication:dp
publication:engr
publication:nano
publication:nanopub
publication:ece
publication:ecepubs
A mathematical model for analyzing the thermal characteristics of a flat micro heat pipe with a grooved wick
Do, Kyu Hyung
Kim, Sung Jin
Garimella, Suresh
A mathematical model is developed for predicting the thermal performance of a flat micro heat pipe with a rectangular grooved wick structure. The effects of the liquid-vapor interfacial shear stress, the contact angle, and the amount of liquid charge are accounted for in the present model. In particular, the axial variations of the wall temperature and the evaporation and condensation rates are considered by solving the one-dimensional conduction equation for the wall and the augmented Young Laplace equation, respectively. The results obtained from the proposed model are in close agreement with several existing experimental data in terms of the wall temperatures and the maximum heat transport rate. From the validated model, it is found that the assumptions employed in previous studies may lead to significant errors for predicting the thermal performance of the heat pipe. Finally, the maximum heat transport rate of a micro heat pipe with a grooved wick structure is optimized with respect to the width and the height of the groove by using the proposed model. The maximum heat transport rate for the optimum conditions is enhanced by approximately 20%, compared to existing experimental results. (c) 2008 Elsevier Ltd. All rights reserved.
2008-09-01T07:00:00Z
text
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https://docs.lib.purdue.edu/nanopub/111
https://doi.org/10.1016/j.ijheatmasstransfer.2008.02.039
Birck and NCN Publications
Purdue University
1192180/oai_dc/100//