Study On The Prepared Aluminum-doped ZnO Transparent Conductive Thin Films

The transparent conductive oxide (TCO) thin films with high transmittanceand low resistivity are widely used in solar battery, panel display, filming ofwindow with special features as well as other fields of optoelectronic devices.Among them, indium tin oxide (ITO) thin film is the most widely usedtransparent conductive oxide thin film. But the usage of ITO thin film isaffected by its high price and toxic substances In in raw materials which has acertain impact on the natural environment and human health. Zinc oxide (ZnO)has many advantages such as abundant raw materials, non-toxic, easy tolithography, good stability in hydrogen plasma, and it not only has high lighttransmittance, but also the doped ZnO has good electrical conductivity. So far,the ZnO thin film has become the new TCO film as an alternative to ITO film toreceive widespread attention. At present, the aluminum-doped zinc oxide(ZnO:Al, referred to as AZO) research and development have become a hotspot.Compared with the rigid AZO thin films, flexible AZO thin films not onlyhave similar optical and electrical properties, but also possess light weight,unbreakable, flexible, easy production of large area, easy to carry and otherunique advantages. This makes the AZO thin films deposited on flexiblesubstrates have became a hot research topic in the direction of development ofelectronic devices to miniaturization, lightweight technology.In this thesis, AZO thin films have been prepared on glass (rigid) and PET(flexible) substrates using RF magnetron sputtering method, respectively.Experimental determination and analysis of the comparative study have beenmade. Main contents are as follows:1. Select the process parameters in the experiment for different substrates.The selected process parameters in the preparation of rigid AZO thin filmscontain sputtering power, working pressure and substrate temperature; Whilethe chosen process parameters in the preparation of flexible AZO thin films aresputtering power, working pressure and deposition time of buffer layer. 2. Within the ranges of process parameters, design parameters using theorthogonal group to prepare rigid and flexible AZO thin films, respectively.Flexible AZO thin films are prepared under room temperature, and the flexiblesubstrate is processed by deposition of homogenization buffer layer.3. Make use of X-ray diffraction (XRD), scanning electron microscopy(SEM), four-probe tester as well as UV-VIS spectrophotometer to test andanalyze the structural properties of the film, the surface morphology, electricalproperties of film, the surface morphology, electrical properties and opticalproperties.4. Make a comparison of the hard AZO thin films and flexible AZO thinfilms prepared under the same conditions on the structure properties, surfacemorphology, electrical properties and optical properties.The experimental results show that Zn and Al exist in the forms of Zn2+and Al3+. In addition, the doping of Al doesn’t change the wurtzite structure andpreferred orientation [002] crystallographic direction of ZnO. With theconditions of sputtering power180W, work pressure0.25Pa, substratetemperature200℃and other conditions the same, the prepared rigid AZO thinfilm obtain best optical and electrical properties. The sheet resistance of the filmis16.11/□and the average transmittance in the visible region is92%. At roomtemperature, with the conditions of sputtering power200W, work pressure0.25Pa, deposition time of homogenization buffer layer5min and otherconditions the same, the best properties of flexible AZO thin films are obtained.The minimum sheet resistance is28.46/□, while the average transmittance isup to93%.The experimental results show that the sputtering power, working pressure,substrate temperature and deposition time of buffer layer have a very importantimpact on the performances of the films; The sheet resistance of flexible AZOthin film is slightly higher than the sheet resistance of rigid AZO thin film, theflexible AZO thin film has better unity performance compared with the rigidAZO thin film; Deposing a certain thickness of the homogenization buffer layercan not only reduce the square resistance of the flexible AZO thin films, butalso not affect the transmittance of the film in the visible region; However, itcan also be seen that deposition of homogeneous buffer layer makes the electrical properties of the flexible AZO thin films worse than those of the rigidAZO thin films which are not deposited buffer layer, which suggests thatflexible AZO thin films need to be more in-depth researched.