Dynamic behavior of OH and its atomic contrast with O adatom on the Ti site of TiO_2(110) at 78 K by atomic force microscopy imaging

摘要

We experimentally observed the dynamic behavior of OH on the Ti site (OH_t) of TiO_2(110) at 78 K in detail by atomic force microscopy (AFM). OH_t was imaged as a dimer shape or a fuzzy round shape corresponding to the motion of OH_t that OH_t swings along the [1-10] direction. The frequency of swing positively responds to the applied bias voltage between the tip and the sample, and it is proposed that the applied bias voltage decreases the barrier of the OH_t transition between two or more equilibrium states. Such specific response of OH_t to the applied bias voltage can be used as the fingerprint. In addition, the atomic contrast of O adatom (O_(ad)) and OH_t is compared with the contrast of other surface species by AFM, and it is demonstrated that the contrast of O_(ad) and OH_t is similar to the contrast of the surface defects due to the effect of tip apex polarity. H atom desorption of OH_t is performed by Kelvin probe force spectroscopy, and it is resulted from the reduction of barrier width together with the tunneling electron excitation. The present study is expected to be useful to explore the property of H-involved species and the surface reactions on the oxide surface by AFM.