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The surface morphology in polycrystalline silicon (poly-Si) film is an issue regardless of whether conventional excimer laser annealing (ELA) or the newer metal-induced lateral crystallization (MILC) process is used. This paper investigates the stress distribution while undergoing long-term mechanical stress and the influence of stress on electrical characteristics. Our simulated results show that the nonuniform stress in the gate insulator is more pronounced near the polysilicon/gate insulator edge and at the two sides of the polysilicon protrusion. This stress results in defects in the gate insulator and leads to a nonuniform degradation phenomenon, which affects both the performance and the reliability in thin-film transistors (TFTs). The degree of degradation is similar regardless of bending axis (channel-length axis, channel-width axis) or bending type (compression, tension), which means that the degradation is dominated by the protrusion effects. Furthermore, by utilizing long-term electrical bias stresses after undergoing long-tern bending stress, it is apparent that the carrier injection is severe in the subchannel region, which confirms that the influence of protrusions is crucial. To eliminate the influence of surface morphology in poly-Si, three kinds of laser energy density were used during crystallization to control the protrusion height. The device with the lowest protrusions demonstrates the smallest degradation after undergoing long-term bending.

Neuromorphic computing with intelligent powerefficient data processing has become an innovative technology to overcome the performance bottleneck of traditional von Neumanntype computing architecture. As an essential element to construct a neuromorphic system, a kind of artificial synapse with high technology maturity, rich functionality, and homeostatic regulation based on simple and robust mechanism is in urgent demand. Here, we propose the dual-gate low-temperature polycrystalline silicon thin film transistor to be a prospective candidate for scalable biomimetic synapse. Fundamental bilingual homosynaptic behaviors, including excitatory postsynaptic current, inhibitory postsynaptic current, and paired pulse facilitation, have been successfully emulated based on the charge trapping mechanism under electric pulse stimulation at either top or bottom gates. The strength of the top-gated induced excitatory and inhibitory responses can be dynamically modulated by the electrical biases at the modulatory bottom gate, indicating the realization of heterosynaptic plasticity. Furthermore, the transition between excitatory and inhibitory modes can be easily controlled by the interplay of the voltage biases at top and bottom gates. These results indicate the commercial thin-film transistor technology could find its novel fundamental role in the emerging artificial intelligence era.

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