Self-Welded Metal-Catalyzed Carbon Nanotube Piezoresistors with Very Large Longitudinal Piezoresistivity of ~ 4×10-8 Pa-1

Self-welded double-wall and multi-wall carbon nanotube (DWCNT and MWCNT) bridges were used for the first time as nano-scale piezoresistors to monitor vibration and deformation of silicon cantilever beams. The CNTs were grown using low-pressure metal-catalyzed chemical vapor deposition technique between silicon-on-insulator posts situated over cantilever beams such that when the beams were deformed, CNTs were axially strained. Telescoping of inner CNT cylinders occurring under these axial strains changed the CNTs resistance. The CNT-post weld strength, as measured using atomic force microscope, was larger than 100 nN/CNT and their full-scale resistance change was larger than 10⁵ Ω. The effective longitudinal piezoresistivity of CNTs was larger than 4×10^-8 Pa^-1 which is more than 10 times larger than that of Π₄₄ in silicon.