Long-term plasticity and inhibition of superlattice-like Sb/Sb2S3-based synaptic devices for neuromorphic computing

Thermal stability and resistance drift are the two main issues for phase change memory (PCM) in application of neuromorphic computing. Though monatomic Sb thin films possess rapid crystallization and mitigate the risk of component segregation, they suffer from poor thermal stability. In this paper, Sb/Sb₂S₃ with a superlattice-like (SLL) arrangement were fabricated by employing pure Sb and thermally stable Sb₂S₃. The crystallization temperature of the Sb/Sb₂S₃ SLL film reaches approximately 226 ^oC. The data retention temperature for 10 years achieves about 137 ^oC and the crystallization activation energy is approximately 3.44 eV. These findings highlight the remarkable thermal stability of these films. The presence of tension at the interface of SLL thin films hinders the growth of Sb crystals. By analyzing the crystallization mechanism, it was found that the crystallization kinetic exponent ($n$$n$) is 0.481, indicating one-dimensional growth of Sb/Sb₂S₃ SLL thin films. This helps reduce nucleation randomness and minimize resistance drift. In addition, we simulated synapses using PCM units based on [Sb(2 nm)Sb₂S₃(4 nm)]₁₆ by applying specific pulse schemes, achieving long-term potentiation (LTP) and long-term depression (LTD) of synaptic weights. The three-layer perceptron device achieved recognition accuracy of 96% in a handwritten digit identification task, suggesting that our approach has the potential to enhance the efficiency of neuromorphic computing networks.