High on/off ratio ZnS-based ReRAM with multi-level switching characteristics

Abstract

Resistive random-access memory (ReRAM) devices based on zinc sulfide (ZnS) were fabricated and characterized. The devices consist of a Ti/Pt bottom electrode (BE), radio-frequency magnetron sputtered 30-nm-thick ZnS switching layer, and a 150-nm-thick Ag top electrode (TE). X-ray photoelectron spectroscopy (XPS) confirmed the chemical composition and identified intrinsic defects in ZnS, contributing to the resistive switching. Electrical measurements reveal stable cycling behavior, high on/off ratio (∼5 × 103), excellent endurance (∼2 × 103 cycles), and good retention (∼6 × 103 s) characteristics. Cycle-to-cycle and device-to-device variability analysis demonstrated low coefficients of variation (CVs) for resistance states and switching voltages, suggesting stable operation and high uniformity. The resistive switching is attributed to conductive filament (CF) formation and rupture driven by Ag ion migration through ZnS bulk defects. Multi-level switching was achieved by controlling the writing current (IW) and evaluated using bit error rate (BER) analysis. The ZnS-based ReRAM exhibited reliable multi-level switching characteristics up to six distinct resistance states, indicating its potential for high-density memory devices. © 2025