Photocatalytic decomposition of organic thin films in a nanometer-scale by an atomic force microscope

Upheavals of adsorbed oxygen molecules are formed on the TiO2 (110) surface by applying a negative bias voltage between the TiO2 and a tip. The heights of upheavals corresponding to the state density of O2- increase with a bias voltage. The letters "YT" constructed from O2- are drawn on the TiO2 surface. The letters have the line width of 22 nm and the height of 6 nm. The letter "T" is selectively deleted by applying a positive voltage under ultraviolet illumination. It is found that the adsorption of O2 and the photodesorption of O2 are controlled in a nanometer scale. A stearic-acid film deposited on the TiO2 (110) is selectively decomposed at the area where a bias voltage of 10 V is applied under ultraviolet illumination. Using AFM-based photocatalysis, several patterns are formed in a thick stearic-acid film. The letters "YT" are drawn in the thin stearic-acid film. The spatial resolution of the photocatalytic decomposition is estimated to be 30 nm from a line width of the letters "YT".