Scanning tunneling microscope study of surface morphology variation of CeO₂(111) with changing annealing condition

The surface morphology variation of CeO₂(111) with changing annealing condition was examined by scanning tunneling microscopy (STM). Hexagonal islands and pits containing two types of step edge have been found as characteristic features in a short-time-annealed surface. We observed that the triangular pits having only one type of step edge increase in number with annealing time, while the hexagonal pits and islands decrease and the deviated hexagonal pits increase. Step edges of the hexagonal pits that have higher coordinative saturation get preferential thermodynamic stability to form triangular pits, the most stable surface structures on the CeO₂(111) surface in the equilibrium stage of annealing. These results have important implications for controlling catalytic activity on ceria.