Flexible ZnO Thin-Film Transistors on Thin Copper Substrate

In this paper, we report the fabrication of flexible ZnO thin-film transistors (TFTs) on the 25-μm-thick copper substrate. The Cu substrate compatible with high-temperature processes was deposited by electroplating, which led to a smooth surface. The ZnO layer was deposited at room temperature, and a thermal annealing process was conducted at 300 °C in the air after the fabrication of TFTs. The threshold voltage, hysteresis-voltage, and contact resistance are improved after annealing, whereas the mobility, subthreshold swing, and ON/OFF ratio are barely changed. The stabilities of ZnO TFTs are also enhanced, evidenced by the smaller threshold voltage shifts induced by positive and negative gate bias stresses. The field-effect mobility, threshold voltage, and subthreshold swing are stable even when exposed to a mechanical tensile strain up to 1.25% and 10000 bending cycles.