Analysis of "on" and "off" times for thermally driven VO₂ metal-insulator transition nanoscale switching devices

Vanadium oxide undergoes a sharp metal-insulator transition in the vicinity of room temperature and there is considerable interest in exploring novel device applications that utilize this phase transition. Using experimentally determined values of the thermal conductivity across the metal-insulator transition in VO₂ thin films, we estimate the switching characteristics of two-terminal VO₂ devices. The minimum switching time for both heating ("on" state) and cooling ("off" state) processes is explored using a simple resistance-capacitance thermal circuit model. The estimated minimum switching time is on the order of ∼1 ns for 20 nm VO₂ films which is comparable to experimentally observed switching times. Optimal operating temperatures to maximize switching times are estimated. Methods to further enhance the switching kinetics by device thickness, carrier doping/strain, interfacial thermal resistance and input thermal energy are discussed. The simulations are compared with a 3-D model for VO₂ devices on Si substrates utilizing COMSOL. The results are of potential relevance to the emerging field of correlated oxide electronics with fast phase transitions.