Nonlinear electrical transport near the metal–insulator transition in V4O7 thin films

Abstract

Nonlinear electrical transport associated with correlated electronic states has been widely investigated in transition-metal oxides near metal–insulator transitions. Here, we investigate nonlinear transport and threshold switching in sputter-deposited V4O7 thin films grown on fused silica substrates. Temperature-dependent transport measurements show a metal–insulator transition near 240 K with negligible thermal hysteresis, defining the temperature scale that governs the nonlinear electrical response. Current–voltage measurements reveal reproducible bipolar threshold switching over a broad temperature range, with the threshold voltage decreasing systematically as the transition temperature is approached. Electrothermal finite-element simulations reproduce the measured switching characteristics and show that switching occurs when localized Joule heating drives a confined region of the device toward the transition temperature. The simulated peak local temperature at threshold lies close to the intrinsic metal–insulator transition temperature of V4O7, establishing that the nonlinear electrical response originates from electrothermal feedback acting on the strongly temperature-dependent conductivity near the transition. These results identify V4O7 thin films as a model correlated-oxide system in which volatile threshold switching emerges from proximity to an extended metal–insulator transition.