Vanadium Oxide Thin-Film Variable Resistor-Based RF Switches

Vanadium dioxide (VO 2 ) is a unique phase change material (PCM) that possesses a metal-to-insulator transition property. Pristine VO 2 has a negative temperature coefficient of resistance, and it undergoes an insulator-to-metal phase change at a transition temperature of 68 °C. Such a property makes the VO 2 thin-film-based variable resistor (varistor) a good candidate in reconfigurable electronics to be integrated with different RF devices such as inductors, varactors, and antennas. Series single-pole single-throw (SPST) switches with integrated VO 2 thin films were designed, fabricated, and tested. The overall size of the device is 380~\mu \text{m}\times 600~\mu \text{m} . The SPST switches were fabricated on a sapphire substrate with integrated heating coil to control VO 2 phase change. During the test, when VO 2 thin film changed from insulator at room temperature to metallic state (low-resistive phase) at 80 °C, the insertion loss of the SPST switch was