The Preparation Of ZnO:Al Thin Films Deposited On Glass Substrate By R.F. Magnetron Sputtering And The Characterization Of Their Structure And Properties

Al-doped ZnO (AZO) thin film is emerging as one of the best potential alternatives to other TCOs, not only due to its comparable electro-optical properties with ITO thin films, but also its costeffectiveness (with inexpensive, abundant raw materials), and environment-friendly nature and more chemical stability than ITO in hydrogen plasma. AZO thin films has been researched and studied a lot. This article creatively utilized homo-buffer layer to improve the micro-structure and electro-optical properties of the films.In this article, AZO thin films were deposited by using R.F magnetron sputtering, the influence of sputtering parameter on the structure and properties of AZO thin films was studied. And AZO homo-buffer layers were deposited under different parameters, the influence of buffer layer thickness and deposition temperature on the structure and electro-optical properties were studied. The obtained results are as follow:1) By XRD patterns, AZO thin films deposited under different parameters showed a highly preferred oriented (002) plane, which was decided by the nature that (002) plane has the lowest surface free energy. By XPS pattern, it was found that only zinc and oxygen exist in AZO thin films, the valence of zinc is+2, and the valence of oxygen is-2, aluminium was not found in the XPS pattern due to its low content.2) The AZO thin films have high transmittance in visible range (80%-85%), and have relatively high reflectance (15%-75%) in middle infrared range in 4000-400cm^-1. The sheet resistance of the films can reach a minimum of about 12Ω/□.3) The insertion of AZO homo-buffer layer can effectively improve the structure and electro-optical properties of the thin films. The buffer layers can minimize the mismatch between AZO thin films and the glass substrates, and reduce the stress in the thin films, and make the grain size larger in the thin film crystals. Homo-buffer layer with appropriate thickness can reduce the sheet resistance of thin films to 37Ω/□and make the ultra-violet cutting-off edge shift from 335nm-324nm, and can increase the reflectance in infrared range to about 70%. The optimal deposition parameters under room temperature are: sputtering power 100W, argon pressure 0.25Pa, and time for sputtering is 5 minutes. The insertion of buffer layer under different substrate temperature is beneficial for both the structure and electro-properties of AZO thin films. With insertion of AZO buffer layer prepared under 300℃, the AZO thin film has the biggest grain size of 28.18nm, and the stress in AZO films was minimized to 0.07601GPa, and the reflectance in infrared range was maximized to about 67%, but the transmittance of the films did not obviously change.