Mechanism of Nonvolatile Resistive Switching in ZnO/α-Fe2O3 Core–Shell Heterojunction Nanorod Arrays

Abstract

Nonvolatile resistive switching based resistive-random-access-memory (RRAM) is evolving rapidly among various other nanoscaled-semiconductor technologies. In this article, resistive switching mechanism in a solution-route-processed ZnO/α-Fe2O3 core–shell n–n heterojunction nanorods (NRs) is investigated for the first time. As fabricated nanostructured electrode shows resistive switching with compelling ON/OFF ratio at a significantly small reverse bias voltage (−0.55 V). Moreover, this core–shell nanorod-based resistive-switch exhibits an excellent time-retention (with relaxation constant (α) ∼ −0.0065 even after ∼103 s) and endurance (with a minute change in switching potential after 100 switching cycles). Resistive switching in this core–shell nanorods system arises due to the tuning of band-alignment at the heterojunction interface governed by fast and reversible migration of charge/ionic species on either side of the interface under reverse-bias condition, facilitating electron tunneling across the interface as supported by experimental observations, together with highly nonlinear dependency of the drift velocities of oxygen-vacancies on applied potential bias. Such understanding behind the high-degree and energy-efficient nonvolatile resistive switching in ZnO/α-Fe2O3 core–shell NRs make them a potential candidate in engineering next-generation nanoheterostructure based RRAM devices.