Physical Review B
We study the thermal relaxation dynamics of VO2 films after the ultrafast photoinduced metal-insulator transition for two VO2 film samples grown on Al2O3 and TiO2 substrates. We find two orders of magnitude difference in the recovery time (a few nanoseconds for the VO2/Al2O3 sample versus hundreds of nanoseconds for the VO2/TiO2 sample). We present a theoretical model to take into account the effect of inhomogeneities in the films on the relaxation dynamics. We obtain quantitative results that show how the microstructure of the VO2 film and the thermal conductivity of the interface between the VO2 film and the substrate affect long time-scale recovery dynamics. We also obtain a simple analytic relationship between the recovery time-scale and the film's parameters.
Rodriguez-Vega, M., Simons, M. T., Radue, E., Kittiwatanakul, S., Lu, J., Wolf, S. A., ... & Rossi, E. (2015). Effect of inhomogeneities and substrate on the dynamics of the metal-insulator transition in VO 2 thin films. Physical Review B, 92(11), 115420.