Role of the crystallinity of ZnO films in the electrical properties of bottom-gate thin film transistors

The strong correlation between the microstructural characteristics of ZnO channel layers grown at various temperatures by radio-frequency magnetron sputtering and the electrical performances of resulting bottom-gate thin film transistors (TFTs) was reported. Transmission electron microscopy revealed that increasing growth temperature enhanced degree of c-axis preferred orientation and enlarged width of columns in the ZnO films. The ZnO channel layers grown at 250 and 350 °C exhibited TFT saturation behavior. However, growing them at ≥ 350 °C produced small grains in the junctions of ZnO/SiO2 interface and grain boundaries, which led to hump behavior in TFT transfer curve caused by formation of additional boundaries.