Grain-boundary-driven stochastic oxide junction in 2D SnSe enables dual electrical-optical PUFs

Abstract Introducing scalable physical entropy into solid-state platforms is a key challenge for secure hardware systems. Here, we present a dual-mode physically unclonable function (PUF) based on grain-boundary-induced oxidation in two-dimensional (2D) tin selenide (SnSe) multilayers. Photo-oxidative activation initiates selective oxidation along grain boundaries, forming spatially random SnSe/SnO₂ oxide junctions without lithographic patterning. This guided disorder transforms uniform polycrystalline films into high-entropy architectures, where nanoscale variations in composition and conductivity arise from the intrinsic microstructure. Electrical measurements reveal device-to-device variability driven by localized junction asymmetry, while optical excitation independently modulates photocurrent responses, enabling dual electrical-optical challenge-response behavior. At optimized oxidation duration, the system achieves maximal entropy and low inter-mode correlation, yielding cryptographically robust and mode-orthogonal keys. Our approach presents a template-free, material-intrinsic strategy for engineering multi-dimensional entropy in 2D semiconductors, offering a scalable pathway toward secure and reconfigurable hardware identifiers.