Nano-photocatalytic decomposition of a stearic acid film deposited on the TiO2 by an atomic force microscope

Stearic acid films have been deposited on single crystalline TiO2 (1 1 0) substrates by vacuum evaporation. No changes are seen in AFM topographic images of the stearic acid films after the scan at a bias voltage of 10 to 10 V in the dark. Similarly, ultraviolet irradiation at a bias voltage <0.0 V brings about no changes of the AFM topographic images. In contrast, a rectangular hole with the size of 200 nm 200 nm is formed in the stearic acid film after the scan at 10 V under ultraviolet irradiation. No current flows on the stearic acid film, whereas an appreciable current flows at 2.0 Vat the rectangular hole. The formation of the rectangular hole results from the field-assisted photocatalytic decomposition of the stearic acid film by AFM