Effect of Plasma Pretreatment of Soda-Lime Glass on the Preferred Orientation of TiO₂ Prepared by PECVD

TiO₂ has environmental application due to its unique photoinduced properties such as antibacterial and superhydrophilic functions, It is reported that crystalline structure and orientation of TiO₂ thin film affect photocatalytic efficiency. And our previous study showed that <112>-preferred orientation TiO₂ film resulted in the better photocatalytic efficiency. <112>-oriented TiO₂ thin films were fabricated on sodalime glass substrate using PECVD methods. This study was the effort to find the correlation between pretreatment with plasma and <112>-preferred orientation of TiO₂ thin films. The PECVD methods were used at the relatively low substrate temperature of the range from 250° to 412° in order to avoid Na⁺ diffusion from the soda-lime glass substrate into TiO₂ layer during deposition. Plasma pretreatment drives soda-lime glass to have high roughness and high surface energy because its contribution to a shift in Si-O- (non-bridging) due to sodium ion depletion at the soda-lime glass surface. And that results are confirmed through the investigation of AFM and contact angle measurement. Pretreatment with plasma was used for changing the surface characteristics of soda lime soda-lime glass to fabricate <112>-preferred orientation of TiO₂ thin films. The facet of the <112>-oriented film consists of {100} and {004} facet planes. {100} facet planes are so unstable that they have the high surface energy because they show no interrupted chain of strong bond, in crystalline TiO₂. <112>-oriented film consisted of {100} facet planes with high surface energy will prefer to be deposited on the unstable substrate with high surface energy better than on the stable substrate. The XRD and SEM results showed TiO₂ thin films deposited on the soda-lime glass pretreated with plasma have a preference of <112>-orientation. Finally, plasma pretreatment drove TiO₂ thin films to have <112>-preferred orientation through improving the surface of soda-lime glass.