Thermally modulated photoelectronic synaptic behavior in HfS₂/VO₂ heterostructure

Neuromorphic computing is known for its efficient computational speed, low latency, and reduced power consumption, which is considered a pivotal technology to overcome the von Neumann bottleneck. Artificial synapses are an indispensable component of neuromorphic computational artificial neural networks. To guarantee effective and precise processing of optical signals, it must have a high responsivity, detectivity, and the ability to adapt to various environments. Here, a synaptic transistor based on the HfS₂/VO₂ heterojunction with a responsivity of 8.6 × 10³ A·W⁻¹ and a detectivity of 1.26 × 10¹⁴ Jones at 405 nm laser was reported. Meanwhile, the typical synaptic behavior was successfully simulated, including postsynaptic currents (PSCs), the transition from short-term plasticity (STP) to long-term plasticity (LTP). When VO₂ converts from the semiconductor state to the metal state, the HfS₂/VO₂ heterojunction transforms into a Schottky heterojunction from a Type II heterojunction with temperature. What's important, the heterojunction still exhibits excellent responsivity and detectivity, as well as stability of synaptic properties. In addition, the classical Pavlovian conditioning experiment is simulated under different laser intensity to study the brain's associative learning behavior. The results demonstrate that the HfS₂/VO₂ heterojunction synapse exhibits significant responsivity and detectivity and is adaptable to high-temperature environments, showing great potential for neuromorphic computational applications. Graphical abstract: (Figure presented.)