Fabrication And Properties Of ZnO Thin Films And ZnO-based Photoelectric Devices

In this paper, ZnO thin films were grown at room temperature on glass and flexible PC substrates using pulsed laser deposition techniques (PLD). The as grown ZnO thin films had good crystalline quality. We had carried on a series of performance characterization, analyzed and discussed influence of the growth parameters especially the oxygen pressures on the ZnO film quality. The results showed that ZnO thin films grown at oxygen pressure of 10-30 Pa had good crystalline quality. For ZnO films grown on glass substrates, the relative higher oxygen pressure was more suitable for the growth of high quality ZnO films. ZnO films grown at 30 Pa had more smooth surface morphology and lower electron concentration, with the resistivity of 387Ωcm. By contrast, for films grown on PC substrates, ZnO films showed stronger near band edge emission peak and resistivity increased to 3.6×104Ωcm as the oxygen pressure decreased from 30 Pa to 10 Pa. ZnO films grown at 10 Pa obtained better optical and electronic properties.On the basis of the research, we fabricated ZnO-TFT and UVD by means of pulsed laser deposition PLD technology, RF magnetron sputtering and electron-beam evaporation technology. We characterized and analyzed the electrical properties of TFT and UVD devices. ZnO-TFT fabricated on PC substrates with top-gate structure had a relatively large leakage current. ZnO-TFT fabricated on glass substrates with bottom gate structure showed n-channel enhancement mode with good saturation output curve. The threshold voltage was about 20 V, and the saturation field-effect mobility was 0.36 cm2V-1s-1.As VGS increased from 0 V to 40 V, TFT current showed the process from off-state to open state, with the maximum current ratio Ion/Ioff 1.9×103,sub-threshold swing 10.4V/decade. In addition, we fabricated electrode photoconductive UVD, which had a dark current of only 300 nA with 5 V bias voltage. The detector response peak was about 379 nm and the the UV-visible rejection ratio was greater than 3 orders of magnitude.