Noncontact Atomic Force Microscopy. Dynamic Behavior of Atoms and Molecules on TiO2(110) and CeO2(111) Observed by Noncontact Atomic Force Microscopy.

Abstract

Our recent studies on metal oxide surfaces by noncontact atomic force microscopy (NC-AFM) are reviewed. We have demonstrated that atom-resolved images of a TiO2(110) surface can be obtained by NC-AFM. We have also revealed that isolated species of formate ions and hydrogen adatoms on TiO2(110) can be imaged by NC-AFM. As an example of observation of dynamic behavior of adsorbed molecules by NC-AFM, images of fluctuating molecules of acetate ions at domain boudaries of (2×1)-acetate overlayer on TiO2(110) are presented. CeO2-x has been believed to play a crucial role in automotive exhaust catalysis with its special oxygen storage capacity. Surface oxygen atoms at an oxygen-terminated CeO2(111) surface, oxygen point vacancies, and multiple oxygen vacancies such as triangular defects and line defects were visualized by NC-AFM. Unexpected high mobility of surface oxygen atoms at room temperature was observed on slightly reduced CeO2(111) with multiple defects. This observation is probably relevant to facile oxidation-reduction cycles of CeO2-x.