Highly tunable multilevel resistive states in VO2/CuInP2S6 heterojunctions combining ionic migration and metal–insulator transition

Abstract

CuInP₂S₆ (CIPS) with its ionic conductivity has attracted increasing attention, due to its great potential in neuromorphic computing and smart memristor devices. Cu⁺ position and its migration behavior play a pivotal role in the control of ionic conductivity, making it imperative to investigate the Cu⁺ migration behavior in CIPS. Herein, we construct a CIPS nanosheet/VO₂ microwire heterojunction and reveal its highly tunable multilevel resistive states. It is worth noting that heterojunction conductivity could be continuously modulated by driving the Cu⁺ ion via a poling bias. Meanwhile, the metal–insulator transition (MIT) behavior in VO₂ leads the transformation between nA-level and μA-level current of the heterojunction via temperature. Due to the built-in electric field induced by the accumulation and depletion of Cu⁺ ions, the CIPS/VO₂ heterostructure exhibits a significant diode-like resistance switching behavior, which is sensitive to the amplitude, duration, and number of cycles of poling bias. Furthermore, temperature-dependent current measurements indicate that the conductivity of the CIPS/VO₂ heterostructure undergoes a change with more than two orders of magnitude when VO₂ transitions into a metallic phase. Through the synergetic contribution of controllable Cu⁺ migration and MIT of VO₂, the current and device performance can be effectively controlled. This work presents an innovative approach for realizing the multilevel resistive states while uncovering potential applications for next-generation neuromorphic computation.