Estimation of the energy barrier responsible for hysteresis and multilevel nonvolatile resistance states in VO2 thin films

We propose a model to estimate the energy barrier responsible for the hysteresis of the thermally driven Mott phase transition. The fitting results are in good agreement with experimental data, where the associated barrier values for ${\mathrm{VO}}_{2}$ films with various hysteretic behavior are determined. For heating to a fixed temperature in the hysteresis, the electric pulse $(\ensuremath{\sim}100\phantom{\rule{0.16em}{0ex}}\mathrm{V}/\mathrm{cm})$ induced responses exhibit steps of the resistance in ${\mathrm{VO}}_{2}$ thin films, forming multiple nonvolatile states, whereas no remarkable changes occur for the cooling case. We propose that the memory ability can be attributed to the barrier in the hysteresis regime and the multilevel resistances induced electrically are associated with the configuration of the metal and insulator domains.