Electromechanical properties of single-walled carbon nanotube devices on micromachined cantilevers

We have investigated the electromechanical properties of single-walled carbon nanotubes (SWNTs) by constructing carbon nanotube transistors on micro-cantilevers. SWNTs and ultra-long carbon nanotubes (UNTs) were grown on free-standing Si_3N4membranes by using chemical vapor deposition, and electrical contacts were generated with electron beam lithography and lift-off. The cantilevers bearing SWNT devices were micromachined so that hybrid cantilevers with various spring constants were fabricated. To measure the electromechanical properties of the SWNTs, precisely controlled forces were generated by a microbalance and applied to the hybrid cantilever devices. Upon bending, the conductances of the metallic and large-gap semiconducting UNTs showed no notable change, whereas the conductances of the small-gap semiconducting UNTs and networks of SWNTs increased. Numerical simulations of bended SWNT made using a multiscale simulator supported the hypothesis that the small-gap semiconducting SWNTs undergo a metallic transformation upon bending.