Electrical-field-driven metal–insulator transition tuned with self-aligned atomic defects

Abstract

Recently, significant attention has been paid to the resistance switching (RS) behaviour in Fe₃O₄ and it was explained through the analogy of the electrically driven metal–insulator transition based on the quantum tunneling theory. Here, we propose a method to experimentally support this explanation and provide a way to tune the critical switching parameter by introducing self-aligned localized impurities through the growth of Fe₃O₄ thin films on stepped SrTiO₃ substrates. Anisotropic behavior in the RS was observed, where a lower switching voltage in the range of 10⁴ V cm⁻¹ is required to switch Fe₃O₄ from a high conducting state to a low conducting state when the electrical field is applied along the steps. The anisotropic RS behavior is attributed to a high density array of anti-phase boundaries (APBs) formed at the step edges and thus are aligned along the same direction in the film which act as a train of hotspot forming conduits for resonant tunneling. Our experimental studies open an interesting window to tune the electrical-field-driven metal–insulator transition in strongly correlated systems.