SCALE SEE and TID Resilient Vanadium Dioxide Phase-Change Material Millimeter-Wave Switches

Graduate student Zachary Brumbach of Georgia Tech presented at the Vanderbilt Seminar Series.

Vanadium dioxide (VO₂) serves as a phase‑change material that undergoes a rapid insulator‑to‑metal transition near 68 °C, making it a compelling candidate for high‑frequency radio‑frequency (RF) switching. Its ability to toggle between a highly resistive state and a low‑loss conductive state addresses the growing demand for broadband, low‑insertion‑loss millimeter‑wave (mm‑wave) switches in satellite communications, radar, and instrumentation systems.
The resource details the fabrication of custom series VO₂ RF switches on sapphire substrates using a DC sputtering process, with device lengths of 3 µm and 6 µm and copper contacts forming coplanar waveguide interconnects. Thermal excitation drives the transition, producing a five‑order‑of‑magnitude change in sheet resistance and an approximately 20 dB shift in RF loss, as evidenced by S‑parameter measurements from DC to 67 GHz that show high transmission in the on‑state and high reflection in the off‑state. Total ionizing dose (TID) experiments conducted in a Co‑60 cell at 27 °C (insulating) and 80 °C (conducting) reveal less than 2 dB degradation in S₁₁ and S₂₁ up to 10 GHz, while DC resistance changes remain modest (≤ 8 % at room temperature, ≈ 40–50 % at elevated temperature) relative to the five‑decade resistance swing. The analysis links radiation‑induced vanadium‑oxygen bond breakage to trap formation, explaining the observed DC shifts without appreciable impact on gigahertz‑scale RF performance.