Condensed Matter Physics Seminar

Integrated Studies of Structural, Electrical, and Mechanical Properties of Individual Carbon Nanotubes by Using a TEM-STM System

Prof. Jianyu Huang
Boston College
Tuesday, April 18, 2006
Higgins 235, 3 p.m.

A transmission electron microscopy (TEM) delivers atomic-scale structural information with no access to the physical property of the characterized materials. On the hand, a scanning tunneling microscopy (STM) explores the physical property down to a single atom level but without internal structural information of the STM probe and the materials being studied. A TEM-STM system, which integrates a full functional STM into a TEM, takes advantage of both the STM and the TEM, enabling simultaneous structural and electric, mechanical, and thermal property study of individual nanotubes, nanowires, and nanocrystals. Two case studies of using the TEM-STM system are presented. First, I probed the transport property of each individual wall within a multiwall carbon nanotubes (MWCNTs) by using an electric breakdown technique. I found that all the walls within a MWCNT are conducting at an end-contact condition, and a MWCNT is a diffusive conductor. Moreover, the different walls within a MWCNT were found to be either metallic, or semiconducting, or exhibiting pseudogap behavior. Second, I conducted tensile-loading experiments on individual carbon nanotubes. I found that carbon nanotubes are extremely ductile at high temperatures, leading to super-elongation and kink motion phenomena. The super-elongation is attributed to the activation of defects and diffusion at high temperatures. The kink motion is explained in terms of dislocation climb and glide. Concurrent transport measurement revealed an electron localization effect in the super-elongated carbon nanotubes.