Properties Of TiO₂Thin Films Prepared By Reactive Magnetron Sputtering

Photocatalysis of semiconductors is a hot topic in research field during the past30years, in which TiO2is one of the most potential applications of photocatalyst for its excellent chemical stability, wear resistance, low-cost and non-toxic. However, there exist many defects in the use of conventional powder photocatalyst, such as easy to agglomerate, difficult to settle, difficult to retrieve and separate after the reaction and so on. TiO2film photocatalysts can be used to overcome these defects and extend its industrial application. The present main method used to prepare TiO2films is sol-gel method. However, the films prepared by this method are uneven in thickness, which affects the optical quality of the films.In this paper, the TiO2thin films are deposited on glass substrate by reactive DC magnetron sputtering. The effect of working pressure, sputtering power, deposition temperature and oxygen concentration on the structure and properties of the films has been investigated. We have analyzed and studied the micro-structure and the property of the photocatalysis of the prepared films by XRD, AFM, UV-visible spectra and other modern test technologies. In addition, we have also analysized the main factors to influence the structure and property of the films. The results are as follows:(1) The growth rate of films and the grain size decreases as the working pressure increasing from1.5Pa to3.0Pa; the as-deposited films are all anatase; the films becomes more and more rough with the increase of sputtering pressure. The photocatalytic experiments show that the photolytic activity of the films decreases and then increases with the increase of sputtering pressure.(2) The deposited rate of the films increases with the increase of the sputtering power in the range of70-100W; the crystal structure of the as-deposited films is the anatase structure, moreover, the sputtering power is larger, the crystallinity of the film is better; the micro-structure of the films is granular. The photocatalytic activity of TiO2thin films increases and then decreases with the increase of sputtering power.(3) The deposition rate is little affected when the substrate temperature increases from200°C to300°C; the crystal structure of all the as-deposited films is anatase. The grain size increases, and the photocatalytic activity first increases and then decreases with the substrate temperature increasing. (4) The deposition rate, crystallinity degree and grain size is gradually decreased with the increase of oxygen flow rate from5%to20%; the structure of the as-deposited films is anatase. At the same time, the change of the oxygen content has also an impact on the film photocatalytic activity to some extent. When the oxygen content is10%or15%, the film photocatalytic activity is smaller, while a higher or lower oxygen content has a greater influence, which is decided by the thickness, the degree of crystallinity and the grain size of the films.(5) The transmittance of the films is generally more than80%. There is a strong absorption peak at about380nm in the spectrum curve, corresponding to the intrinsic absorption of the TiO2film, which shows that the films have a good absorption effect in the range of UV. The substrate temperature affects the transmittance of the films in some degree, which is mainly related to the structure, grain size, surface roughness and the crystallinity degree of the films. The band gap of the films broadens with the increase of the substrate temperature in some degree, which was mainly due to quantum size effect of the nano-scale TiO2thin films.