Electron impact processes in voltage-controlled phase transition in vanadium dioxide thin films

A study of the voltage-controlled phase transition mechanism in vanadium dioxide thin films was performed in the temperature range 65 – 295 K. Temperature-induced variation of I-V characteristics indicates the type of conductivity defined by space-charge limited currents (SCLC). Based on the analysis of the temperature dependence of sample resistivity, it was found that the dominant transport mechanism is a small polaron hopping conduction. The results of modeling together with obtained experimental data justify the influence of the parameters of trap distribution, associated with oxygen vacancies and hydrogen impurities, on the mechanism of the instability development in vanadium dioxide thin films. At relatively low trap density, the phase transition is more likely initiated electronically. At temperatures below 100 K an appearance of switching with memory is observed. An increase in the trap concentration provokes the prevalence of thermal process in the phase transition triggering.