Photoinduced Redox Reaction Coupled with Limited Electron Mobility at Metal Oxide Surface

Photoinduced oxidation of trimethyl acetate (TMA) was examined on an atomically flat surface of rutile TiO 2 . The macroscopic rate of reaction (the partial pressure of desorption products) was temporary modulated when a TMA-covered surface was UV-irradiated in oxygen gas. Scanning tunneling microscope imaging revealed spatially modulated distribution of TMA and OH on that surface. The limited surface mobility of electrons photoexcited and trapped at OH-associated Ti sites was proposed to cause the temporal and spatial modulations. The characteristic length of the spatial modulation, i.e., the lateral dimension of electron confinement, was a few lattice constants of the oxide.