Self-heating-induced electrical and optical switching in high quality VO2 films controlled with current pulses

Self-heating (SH)-induced electrical and optical switching in high quality VO2 films grown by magnetron sputtering on a c-cut sapphire substrate has been investigated under various applied constant current pulses (I-D). The effect of SH on the behavior of electrical conductivity (sigma), optical transmittance ((T) over tilde), and film temperature (T) examined by applying a constant current pulse of various magnitudes with a pulse duration of five seconds (Delta t = 5 s) in VO2 films which were pre-heated to and stabilized at 57 degrees C, at the brink of insulator-to-metal transition (IMT). The SH effect that arose from the application of constant I-D pulses led to a significant increase in T and substantial changes in sigma and (T) over tilde. Observations showed that, depending on the magnitude of I-D, the sigma and (T) over tilde demonstrate strikingly different temporal behavior not only during the SH-induced IMT but also after the removal of I-D. The observed phenomena could be explained using a simple model based on percolation theory previously proposed for the present system. The outcome of the model is confirmed by the results of the structural IMT obtained by Raman micromapping.