VO2 Phase-Transition-Based Vertical MEMS Microactuators

A vertical multilayer VO2 MEMS microactuator device is reported in this work. A 150-nm-thick VO2 layer is sandwiched between the top Pt and bottom indium tin oxide (ITO) electrodes. An equivalent thermal circuit is developed with a thermal response time of 0.39 ms. With the insulator-to-metal phase transition of VO2 at ~68 °C accompanied by large electrical and lattice changes, a 35- $\mu \text{m}$ -long VO2 actuator experiences 2- $\mu \text{m}$ deflection across the phase transition driven by heating and 0.22- $\mu \text{m}$ deflection when electrothermally actuated. The COMSOL finite element analysis is performed to determine the spatial distribution of the current flow and temperature profile and to verify the experimental measurements of strain-induced bending in this multilayer vertical structure. The obtained experimental result shows a good fit with the simulation analysis, which can in future be used to develop a generic understanding of such vertical MEMS devices.