Study Of Preparation And Characteristics Of Metal-Doped ZnO:Li Thin Films Deposited By Magnetron Sputtering

ZnO thin films have good properties, such as high melting point, the wide band-gap, large exciton binding energy and higher transparency. For Li-doped ZnO (ZnO:Li) thin films, Li doping make the film has the enhanced resistivity (>107Ω.cm), change from the n type conduction caused by the inherent defects in ZnO thin film to the p-type conduction, and has both ferroelectricity and ferromagnetism. For metal-doped ZnO:Li thin films, metal and Li co-doping make not only the conduction type of ZnO film change, but also the electrical, optical and magnetic properties further enhance.ZnO:Li films with different Li content are prepared on Si (100) at different argon/oxygen ratio, working pressure, sputtering power by using the magnetron sputtering method. Base pressure is lower than5×10-4Pa and target-substrate distance is kept at7cm. ZnO:Li thin films have ZnO wurtzite structure and high c axis preferred orientation. The second phase of Li is not found in the films, and the (002) diffraction peak shifts to low degree with the increase of the Li content. The lattice constant of ZnO:Li films are increased due to Li doping, incateding that Li atoms have been doped into the ZnO lattice. ZnO:Li films have the smooth and dense surface morphology, and their reflectivity is high in the visible range.Then, the metals (Co, Cu, Al)-doped ZnO:Li films are deposited by magnetic sputtering. Using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), vibrating sample magnetometer (VSM) and ultraviolet-visible-near infrared spectrophotometer (UV-VIS-NIR) the structure, surface morphology, magnetism and optical properties of the films are measuremented.The result shows that the crystallization quality becomes bad and the grain size becomes smaller due to Co and Cu doping into the ZnO lattice. All the samples show room temperature ferromagnetism, showing that magnetic source is not from the inherent ferromagnetism of magnetic metal Co, but from the defects caused by metal doping into the ZnO lattice. The saturation magnetization intensity increases from3.67emu/cm3emu to5.78emu/cm3emu, and the coercive force increases from70Oe to82Oe after annealing for Co-doped ZnO:Li films. The magnetism does not significantly change before and after annealing for Cu-doped ZnO:Li films.Al-doped ZnO:Li thin films show the ZnO wurtzite structure (002) peak, there are no peaks related to AI, indicating that Al atoms have been doped into ZnO lattice. The films have the smooth surface and dense structure. With the incorporation of Al, the reflectivity of samples increases, many reflection peaks turn to a single reflection peak in the visible range, and the maxmal reflectivity reachs to99.7%. Al doping make the optical properties of the thin films to be improved.