Electric field-assisted resonance frequency tuning in free standing nanomechanical devices for application in multistate switching using a phase change material

Abstract

VO₂ possesses a unique property of solid-state phase transition near room temperature wherein it transforms from monoclinic (M1) to tetragonal phase (R) that alters its physical properties, such as resistivity, mechanical modulus, and lattice strain, at an ultrafast time scale known as MIT. Such a phenomenon offers a distinct advantage to use VO₂ in switching applications using heat flux as a stimulus. However, such alteration in properties can also be triggered under an electric field (E), which is known as E-MIT. A nanomechanical resonator coated with VO₂ recently received traction where the resonance behavior can be modulated by taking advantage of its phase transition. Herein, we demonstrate that by fabricating a microstring of 400 μm (L) × 5 μm (W) × 240 nm (t) of suspended SiN_x coated with VO₂, the frequency (f_r) of the resonator can be modulated by applying an electric field. We show that at room temperature, the f_r of the microstring can be either reduced (by 0.5% at 15 V mm⁻¹) or enhanced (by 2.2% at 25 V mm⁻¹) or can be varied in a cycle under E-field. Using theoretical models, we establish the simulated results and explain the processes behind it, which demonstrate excellent mechanical tuning properties of the VO₂-based microstring resonator, making it an attractive and alternative option for highly efficient MEMS-based switches and neuromorphic devices.