Atomistic simulations of material damping in amorphous silicon nanoresonators

Atomistic simulations using molecular dynamics (MD) are emerging as a valuable tool for exploring dissipation and material damping in nanomechanical resonators. In this study, we used isothermal MD to simulate the dynamics of the longitudinal-mode oscillations of an amorphous silicon nanoresonator as a function of frequency (2 GHz-50 GHz) and temperature (15 K-300 K). Damping was characterized by computing the loss tangent with an estimated uncertainty of 7%. The dissipation spectrum displays a sharp peak at 50 K and a broad peak at around 160 K. Damping is a weak function of frequency at room temperature, and the loss tangent has a remarkably high value of similar to 0.01. In contrast, at low temperatures (15 K), the loss tangent increases monotonically from 4 x 10(-4) to 4 x 10(-3) as the frequency increases from 2 GHz to 50 GHz. The mechanisms of dissipation are discussed.