Spontaneous Degradation of Flexible Poly-Si TFTs Subject to Dynamic Bending Stress

An abnormal spontaneous degradation of polycrystalline Si thin-film transistors (TFTs) subject to dynamic bending stress is reported. Dynamic mechanical bending along either the channel-width or length direction causes degradation in flexible low-temperature polycrystalline Si TFTs, such as on-state current increase and threshold voltage positive shift. However, after the mechanical stress is removed, TFTs stored in a normal ambient continue to degrade spontaneously, with similar degradation behaviors. The amount of spontaneous degradation can be larger than the mechanical bending-induced degradation and is the most significant for a moderate number of bending cycles. The spontaneous degradation is a new challenge to TFT reliability under mechanical stress.