Ultraviolet light irradiation on a rutile TiO₂(110) 2x1 surface observed by scanning tunneling microscopy

Masahiko Tomitori, Nobuko Edo and Toyoko Arai

School of Material Science
Japan Advanced Institute of Science and Technology

Titanium dioxide (TiO₂) has been widely used as a photocatalyst, which is reactive under ultraviolet (UV) light irradiation. Since catalytic reaction is thought to be site dependent on the catalyst surface, it should be observed by high-resolution surface microscopy on an atomic scale. Using a scanning tunneling microscope (STM), we have observed a rutile TiO₂(110) surface under the UV light irradiation of 365 nm and a power density of 50 ｵW/cm². The surface was prepared to be clean by a cycle of annealing at 870 K in an ultrahigh vacuum and Ar ion sputtering of 1.8 keV, leading it to exhibit a 2x1 reconstruction with a cross-link structure. The wide bright row in the [001] direction near a step edge was split into two thin rows by the irradiation, which look like a complete 2x1 periodicity: oxygen atoms in the wide row are possibly removed cooperatively.