2 pm on Friday, 
February 13th 2009	
Rogers room (PSC 409)

Tarek K. Ghanem
Length-dependent transport measurements in long channel carbon nanotubes 

In order to understand the intrinsic electronic properties of carbon 
nanotubes, it is important to eliminate the contact effects from the 
measurements. This can be accomplished by using a conductive-tip atomic 
force microscope cantilever as a local electrode to obtain length-dependent 
transport measurements. In this talk, I will review the previous 
experimental efforts in this area. I will describe how to obtain a 
reproducible and stable electrical contact between conductive AFM 
cantilevers and carbon nanotubes. I will report on resistance versus 
length R(L) measurements in long channel carbon nanotubes (up to 130 mkm) 
at room temperature. For semiconducting carbon nanotubes in the on-state, 
R(L) is linear. In the depleted state, R(L) is linear for long channel 
lengths (>10 mkm), but non-linear for short channel lengths due to the 
long depletion lengths in one-dimensional semiconductors. Transport 
remains diffusive under all depletion conditions, due to both low disorder 
and high temperature.