Research On Preparation And Optical Character Of Si-doped ZnO Film

Zinc oxide (ZnO) is an II-VI wide band gap (Eg=3.37 eV) semiconductor material with wutzite structure. It has many advantages, such as better chemical stability, the large exciton binding energy of 60 meV, rich sources and low prices. Therefore, ZnO as a multi-functional semiconductor material has a wide range of applications. In order to meet the requirements of the device, especially in the photovoltaic requirements, it is trying to ZnO doped with various elements to modulate its optoelectronic properties. It has been reported in many literatures about broadening band gap of ZnO. However, all the reports are modulating conduction band of ZnO through the doped method. It is since that the ZnO valence band is determined by O 2p state, which is the deeper level. In the current well-known material, only the SiO2 valence band is lower than ZnO. Based on this, the Si-doped ZnO may be made the valence band move to the low-energy. It is of great significance to achieve a high injection efficiency of the ZnO-based light-emitting devices.Si-doped ZnO is prepared in different concentrations by magnetron sputtering method, which using ZnO ceramic target and quartz substrate. Then the Si-doped ZnO samples under the oxygen atmosphere have respectively done with the rapid annealing and with the natural annealing at different temperatures. In order to contrast, undoped ZnO films are prepared by the same preparation method. Through the X-ray diffraction, Raman spectroscopy, photoluminescence spectra and absorption spectra, its structure and optical properties are characterized.By analyzing X-ray diffraction and Raman spectroscopy, it is proved that Si has been doped in the ZnO lattice. By comparing photoluminescence spectra of the undoped ZnO thin films and different concentrations of Si-doped ZnO thin film, it is draw a conclusion that Si-doped led to the UV emission peak of ZnO moving to the short-wave, which can be judged, Si-doped ZnO can increasing band gap. Analysis of absorption spectra also can get the same conclusion. From Chris G Van de Walle, etc. first-principles calculation results, Si may lower the ZnO valence band top and wider its band gap.At the same time, Si-doped also has a major impact on the visible luminescence of ZnO. After 700℃annealing under oxygen atmosphere, the ultraviolet light-emitting of undoped ZnO thin film enhanced, while the visible light-emitting weakened, and the center of visible light-emitting have be blue shift. For the Si-doped ZnO thin films, the blue shift of visible light-emitting center is also observed in the annealing process, the more doping concentration, the higher the annealing temperature. This indicates that Si-doped is a strong interaction with ZnO visible light-emitting deep-level defects...