Low-Leakage Volatile Threshold Switching in Gr/CIPS/h-BN/Au van der Waals Heterostructure via Atomic-Scale Geometric Confinement

Volatile Threshold Switching (TS) devices are critical selector components for suppressing sneak path currents in high-density crossbar arrays. However, active-metal-based TS devices often face the challenge of stochastic conductive filament overgrowth. In this work, we report a high-performance TS device based on a Graphene/CuInP₂S₆/h-BN/Au van der Waals heterostructure. By utilizing hexagonal Boron Nitride (h-BN) as an atomic-scale ion sieve, we achieve atomic-scale geometric confinement of Cu filament growth. The device exhibits excellent unipolar switching characteristics, featuring a high on/off ratio (>10 5 ), ultra-low off-state leakage current (~pA), and a steep subthreshold swing (<15 mV/dec). Mechanistic investigations reveal that the h-BN layer confines the filaments to the atomic scale, causing the metastable filaments to spontaneously rupture upon bias removal due to Rayleigh instability, thereby enabling rapid self-resetting. This interface engineering strategy effectively addresses the filament overgrowth issue, providing a reliable solution for low-power neuromorphic computing hardware.