Electrical transport studies of individual multiwalled carbon nanotubes
Abstract
Electrical transport properties of individual multiwalled carbon nanotubes (MWCNTs) with diameters greater than 50 nm are investigated. MWCNTs grown by both chemical vapor deposition (CVD) and plasma-enhanced chemical vapor deposition (PECVD) methods have been studied. Electrical failure at high currents is observed and described in detail. Our results are consistent with a model of current transport in PECVD-grown MWCNTs that suggests current flow occurs predominantly through a majority number of shells. We infer that this behavior is due to the existence of a large number of defects in the MWCNT. A correlation between growth temperature and electrical resistance of the MWCNTs grown by PECVD is established. The study identifies a temperature window for growing higher-quality MWCNTs with fewer defects and lower resistance by PECVD. A growth temperature near 900°C is suggested as the most favorable temperature for the PECVD growth of MWCNTs. Electrical contact properties between an individual MWCNT and a metal film are investigated using a novel laser ablation contact cutback technique. This innovative technique allows one to systematically and sequentially shorten the contact length formed by an evaporated metal film to a MWCNT. A semiclassical transport model is developed that allows estimates of the linear resistivity of the nanotube as well as the specific contact resistivity between the nanotube and metallic film. The laser ablation contact cutback technique is significantly improved by using a focused ion beam (FIB). The FIB allows higher precision in cutting contacts than possible with laser ablation. This improved 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. A systematic study shows that MWCNTs grown at 900°C by PECVD have comparable electrical properties to MWCNTs grown by CVD.
Degree
Ph.D.
Advisors
Reifenberger, Purdue University.
Subject Area
Condensed matter physics
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.