Polysilicon-filled carbon nanotube grass structural material for micromechanical resonators

Folded-beam capacitive-comb-driven micromechanical resonators constructed of polysilicon-filled carbon nanotube (CNT) grass structural material have been characterized via electrical measurement to extract numbers for mechanical properties. The process used here is based on that first demonstrated in, but improved by introduction of a guiding oxide mold and post-fabrication in situ localized annealing. Specifically, the measured frequency response for a 28.658-kHz in situ localized annealed version yields a Q of 3,230 twice as high as that of an un-annealed one; and an acoustic velocity of 9,042m/s slightly higher than the 8,024m/s of polysilicon, and inching towards the ~12,000m/s typical of SiC. This material not only facilitates fabrication of high aspect-ratio microstructures, but also shows potential (via its silicon-carbon makeup) for approximating SiC, for which theory predicts frequency and Q advantages over silicon for resonant devices.