Epitaxial VO₂ thin film-based radio-frequency switches with thermal activation

In this paper, we report on the demonstration of thermally triggered "normally ON" radio-frequency (RF) switches based on epitaxial vanadium dioxide (VO₂) thin films with a SnO₂ template on (001) TiO₂ substrates. Fast insulator-to-metal phase transition of the epitaxial VO₂ at a relatively low temperature allowed RF switches made of the VO₂ to exhibit sharp changes in the RF insertion loss during cooling and heating at 60 °C and 66 °C, respectively. The change of RF insertion loss due to phase transition is greater than 15 dB. The VO₂ RF switches also completed the transition of S₂₁ within less than 3 °C and showed a low-loss operation frequency of up to 24.2 GHz with a low insertion loss of -1.36 dB and isolation of 17.56 dB at 12.03 GHz, respectively. The demonstration suggests that epitaxial VO₂-based RF switches can be used in switching elements up to Ku-band RF circuits.