Intrinsic Nonlinearity Modulation in Two-Dimensional (Cu,Ag)InP₂S₆ for Selectorless Nonvolatile Memory Array

Selectorless resistive random-access memory is essential for scaling high-density crossbar arrays, yet suppressing sneak path currents (SPCs) without external selector components remains a major challenge. In this work, we investigated a two-dimensional (2D) van der Waals (vdW) mixed cation crystal Cu_0.5Ag_0.5InP₂S₆ (CAIPS) as a switching layer and systematically compared its resistive switching with CuInP₂S₆ (CIPS) and AgInP₂S₆ (AIPS). The coexistence of Cu⁺ and Ag⁺ ions produces asymmetric out-of-plane diffusion barriers, as confirmed by first-principles density functional theory (DFT) calculations, leading to self-rectifying transport and the intrinsic suppression of leakage in arrays. CAIPS-based devices exhibit stable bipolar resistive switching, a high intrinsic nonlinearity factor (>10 under a V/3 read scheme), a large memory window (>9× at V_read = 0.1 V), and low variability (coefficient of variation down to 5.1%), surpassing the performance of both CuInP₂S₆ (CIPS) and AgInP₂S₆ (AIPS). These features, combined with low operational switching voltages, robust endurance, and built-in nonlinearity highlight CAIPS as a promising material for scalable selectorless memory arrays, with direct relevance to energy-efficient neuromorphic and edge-computing architectures.