A surface micromachined light modulator based on vanadium dioxide array

Vanadium dioxide (VO₂) thin film undergoes a semiconductor-to-metal phase transition at about 68°C, which is accompanied with an abrupt transformation from a transparent semiconductor phase to a highly reflective metallic state. To exploit this phase-transition related thermo-optical switching, low-thermal-mass pixels suspended with long and thin legs were micromachined above substrate to achieve good thermal isolation between pixels and fast enough switching speed. VO₂ thin film was fabricated by e-beam evaporation of vanadium metal film followed by oxidation. It exhibits a grain structure and undergoes a phase transition at 65°C. A surface micromachining process was developed to realize a light modulator in 64×64 array. The testing results demonstrate the light switching and modulation ability of the VO₂ array. Further study shows that acceptable optical properties have been maintained throughout the micromachining process.