Effects of Sputtered High-Energy Particles on the Structure and Photocatalytic Performance of TiO₂ Films Prepared by a DC Reactive Sputtering Method

Abstract

By using the Kevin–Meyer formula, we calculated the energy of the high-energy particles (recoil argon ions and negative oxygen ions) that are unique to sputtered thin-film formation when they arrived at a substrate during the sputtering process. We found that the energy of the high-energy particles arriving at the substrate decrease if total gas pressure increases, whereas the photocatalytic performance of a TiO 2 film increases if the total gas pressure increases. We also found that as total gas pressure increases, the surface morphology changed from a gap-free structure to a porous structure in which subgrains were observed. Accordingly, the average surface roughness ( R a ) and surface area ( S ) of the thin film increased. The number of defects, mainly oxygen defects, in the forbidden band also changed depending on the energy of the high-energy particles. Therefore, it was found that the high-energy particles affect the surface area of the TiO 2 thin films and the formation of defects in the thin films, which consequently influences the photocatalytic performance.