The Electrical And Optical Properties Of ZnO Nano-flim Prepared By Magnetron Sputtering

The hexagonal wurtzite structure ZnO is a typical II-VI semiconductor material which owns a wide and direct band gap. At room temperature, ZnO has a quite high exception binding energy (60meV) and the value of band gap is about 3.37eV. ZnO has been widely used in a variety of light-emitting devices, pressure sensitive devices, transparent electrodes and solar window materials, even the military, biological, medical and other aspects owing to its all kinds of morphologies and excellent electrical, optical, magnetic properties.In this paper, magnetron sputtering method was used to prepare ZnO films. In the experiments, ZnO ceramic target was sputtering material and a mixed gas of argon and oxygen was used as sputtering gas. Through adjusting experiment parameters such as working pressure, substrate temperature, sputtering power and the flow ratio of argon and oxygen, ZnO films with a higher (002) peak preferential orientation was successfully prepared. X-ray diffraction (XRD) and scanning electron microscope (SEM) were applied to analyze the influence of experiment parameters on the preferential orientation and surface morphology. It turned out to be that sputtering power had the greatest impact on preferential orientation of (002) diffraction peak. The intensity of (002) diffraction peak first increased and then decreased with the increase of sputtering power and it reached the highest value when the sputtering power was 250W. The intensity of (002) peak augmented continuously with the annealing temperature increased from 300℃ to 600 ℃.According to the result of orthogonal experiments which used to prepared pure ZnO films, Co, Cu single doped and Co-Cu co-doped ZnO thin films were also prepared. Hall effect measurement system was used to analyze the effect on electrical properties of doped ZnO films resulting from the change of doping type and doping concentration. The result showed that when the doping concentration was low, the samples still had hexagonal wurtzite structure and better preferential orientation but when the doping concentration became too high some other diffraction peaks and impurity phases appeared. Cu doped ZnO films presented p-type conductivity and Co doped ZnO films presented n-type conductivity. Co-Cu co-doped ZnO thin films showed p-type conductivity as well, besides the co-doped samples had more uniform morphology. In addition the co-doped samples had lower resistivity compared with Cu single doped ZnO thin films.