High-speed solid-state thermal switches based on vanadium dioxide

Using the phase transformation at 68°C found in materials based on vanadium dioxide, devices exhibiting an S-type current-voltage characteristic have been produced. The characteristic has an unstable differential negative-resistance region which leads to fast switching (20 ns). Devices have been made by the fusion of mixtures of vanadium pentoxide with other oxides on to thin wires in a reducing atmosphere, by depositing vanadium dioxide particles between conductors using a dilute varnish suspension, and by reactive sputtering of vanadium in low oxygen pressures to give thin films.

Theoretical expectations based on a thermal explanation are in good agreement with the observed static and dynamic characteristics. A total cycle time of 700 ns has been obtained, most of which is derived from the turn-off time. On/off resistance ratios over 1000 have been observed.