Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Mechanical Engineering

First Advisor

Xianfan Xu

Committee Chair

Xianfan Xu

Committee Member 1

Minghao Qi

Committee Member 2

Cagri Savran

Committee Member 3

Yi Xuan

Committee Member 4

Peide Ye


Silicon nanowires are promising building blocks for high-performance electronics and chemical/biological sensing devices due to their ultra-small body and high surface-to-volume ratios. However, the lack of the ability to assemble and position nanowires in a highly controlled manner still remains an obstacle to fully exploiting the substantial potential of nanowires. Here we demonstrate a one-step method to synthesize intrinsic and doped silicon nanowires for device applications. Sub-diffraction limited nanowires as thin as 60 nm are synthesized using laser direct writing in combination with chemical vapor deposition, which has the advantages of in-situ doping, catalyst-free growth, and precise control of position, orientation, and length. The synthesized nanowires have been fabricated into field effect transistors (FETs) and FET sensors. The FET sensors are employed to detect the proton concentration (pH) of an aqueous solution and highly sensitive pH sensing is demonstrated. Both top- and back-gated silicon nanowire FETs are demonstrated and electrically characterized. In addition, modulation-doped nanowires are synthesized by changing dopant gases during the nanowire growth. The axial p-n junction nanowires are electrically characterized to demonstrate the diode behavior and the transition between dopant levels are measured using Kelvin probe force microscopy.