Nanomechanical tuning forks fabricated using focused-ion-beam chemical vapor deposition

Abstract

A theoretical and experimental investigation of nanomechanical tuning forks showed them to be mechanical resonators with high quality factors (Q-factors). For the theoretical calculation of resonant frequencies, the arm of a tuning fork was modeled by a beam connected to one or more torsional springs. Tuning forks with arm lengths of 3.6–6.9 μm were fabricated using focused-ion-beam chemical vapor deposition, and their resonant frequencies and Q-factors were measured with an optical instrument. The resonant frequencies calculated for vibrations in the two fundamental modes of the tuning forks (in-phase and antiphase) agreed well with the measured ones. When measured under mild vacuum (10 Pa), Q-factors for the tuning forks vibrating in the antiphase mode were as much as twice as high as those for nanomechanical cantilevers and tuning forks vibrating in the in-phase mode. In contrast, under atmospheric pressure, the Q-factors for the tuning forks vibrating in the in-phase mode were higher than those for the cantilevers and tuning forks vibrating in the antiphase mode for the same resonant frequencies. The high Q-factors in the in-phase mode are due to strong interaction between nanomechanical resonators and ambient air. The results indicate that nanomechanical resonators operating in air can have high Q-factors if their components vibrate in phase.