The Structural And Optical Properties Of Al Doped ZnO Thin Film By DC And RF Magnetron Sputtering System

ZnO is a new-type semiconductor with a direct wide-band-gap of 3.37eV at room temperature. It has a high exciton binding energy of 60meV and hexahedron wurtzite structure at the air condition. It has been investigated extensively because of its interesting electrical, optical and piezoelectric properties making suitable for many applications such as light emitting diodes, photodetectors, electroluminescence, transparent conductive film, surface acoustic waves device and so on. ZnO films have been grown by various deposition methods including magnetron sputtering, molecular beam epitaxy, metal organic chemical vapor deposition and sol-gel process. Magnetron sputtering method is widely used by the researchers because the equipment is simple, low cost, easy operation, high rate of deposition, the requirement of base temperature is lower and good film adhesion, it's ingredients in a certain extent controllable, etc.In this thesis, Al-ZnO films doped with different Al concentration are prepared on glass substrate by DC magnetron sputtering and RF magnetron sputtering system at the same condition. In this way some experimental data and the theoretical basis are provided for the application of ZnO films. The results are summarized as follows:1. Al-ZnO films doped with different Al concentration are prepared on glass substrate by RF magnetron sputtering system. We have investigated the influence of the different Al concentration on the microstructure and optical properties of ZnO films. The results show that all the samples have a strong diffraction peak and high preferential orientation in the (0 0 2) crystallographic direction. There are a very smooth surface and obvious grain boundaries. The transmission spectrum and absorption spectrum of Al-ZnO show that Al-ZnO films possess a transmittance of about 85% in the visible region and the transmittance decrease with increasing Al concentration. The optical band edge shift to a shorter wavelength first as Al is incorporated, and then to a longer wavelength with the increasing of Al content. The optical band gaps are calculated based on the quantum confinement model are in good agreement with the experimental values. 2. Al-ZnO films doped with different Al concentration are prepared on glass substrate by DC magnetron sputtering system. We have investigated the influence of the different Al concentration on the microstructure and optical properties of ZnO films. The results show that the sample of undoped ZnO film have a strong diffraction peak and high preferential orientation in the (0 0 2) crystallographic direction. This is a single crystal. After doped Al atom, the films have the three diffraction peaks which are (1 0 0),(0 0 2),(1 0 1) , respectively. The transmission spectrum and absorption spectrum of Al-ZnO show that Al-ZnO films possess a transmittance of about 82% in the visible region. The optical band edge shift to a shorter wavelength first as Al is incorporated. On the Al-ZnO film, affecting the transmission rate of films is free carrier, with the increase of doping content, the transmission rate drops, and RF magnetron sputtering Al-ZnO film transmittance have the same results. While undoped ZnO thin films did not show lower than the transmission rate after doping, we believe that this and the film's uneven and the film and the substrate interface. Obtained by linear fitting, as the doping increases, the value of optical band gap increases, absorption edge blue shift, which is consistent with the transmission. Calculated according to the quantum confinement model of the optical band gap value of the sample and the linear regression from the optical band gap value although no exact data, but exactly the same trend, the quantum confinement model can better explain the Al doping ZnO optical band gap change.