Photoinduced surface roughness variation in polycrystalline TiO2 thin films

Photoinduced microstructural changes in transparent anatase thin films with large-grain polycrystallites (−200 nm) were evaluated using atomic force microscopy (AFM). Films were subjected to a vacuum ultraviolet (VUV) pretreatment before heating at 500 °C. Photoinduced wettability of the films was subsequently confirmed. Upon UV illumination, the surface image became blurred with an apparent increased surface roughness. The image sharpened gradually as the surface returned to its initial state. This microstructural surface change is most pronounced at grain boundaries.