Effects Of Al Doping Density, Substrate And Annealing Time On The Properties Of ZnO Thin Films

Aluminum-doped zinc oxide(AZO)thin films with low resistivity and high transparency in visible range are promising as alternatives to ITO for transparent conducting oxide(TCO), since indium is a very expensive and scarce material, while AZO, the source materials of which are inexpensive and non-toxic, is the best candidate. Nowadays, various technologies have been reported to produce AZO thin films, and magnetron sputtering with high deposition rate and uniformity is considered to be one of the most important methods for preparing AZO thin films.In this thesis, AZO films doped with different Al concentration are prepared on glass substrate by 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. AZO 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 the sample of undoped ZnO film has a strong diffraction peak and high preferential orientation in the (002) crystallographic direction. This is a single crystal. After doped Al atom, the films have the three diffraction peaks which are(100),(002),(101), respectively. The transmission spectrum and absorption spectrum of AZO show that Al-ZnO films possess a transmittance of about 85% 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 DC 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 believed that it has connection with the film's uneven and the interface between the film and the substrate material. 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. The optical band gaps calculated based on the quantum confinement model are in good agreement with the experimental values. Therefore, the quantum confinement model can better explain the change of optical band gap of Al doping ZnO.