Nanofabrication and electrostatic operation of single-crystal silicon paddle oscillators

We report the fabrication and characterization of paddle oscillators featuring nanometer-scale supporting rods. The devices show two resonances in the 1-10 MHz range, which we attribute to the translational and torsional modes of motion. While the frequency response of the translational motion shows evidence of nonlinear behavior, the torsional response remains symmetric throughout the range of excitation. We present a model for the electrostatic excitation of the two modes. Torsional motion is induced via asymmetries of the system, and amplified by a modulation of the effective torsional constant. The model of the translational motion predicts a nonlinear behavior for displacements as small as 15 nm. Analysis of both modes of motion consistently suggests structures softer than expected from bulk silicon. Quality factors approaching 10³ are measured.