Controllable Manipulation of the Surface Superstructures and Stoichiometry of Single-Crystal CoO(001)

The surface stoichiometry of transition-metal oxides plays a vital role in their physical and chemical properties. However, the controllable manipulation of the surface stoichiometry on the host still remains a challenge. Herein, the surface stoichiometry of single-crystal CoO(001) surfaces was manipulated in combination with high-energy Ar+ ion sputtering and high-temperature annealing. Two types of superstructures with large periodic lattices (10×10)R18.4° and (32×32)R45° were detected by microchannel plate–low-energy electron diffraction (MCP-LEED). The presence of the superstructure associated with the defects (here more likely to be oxygen vacancies), rather than the reconstruction, was further verified by the vibrational frequency fingerprint of CO probing molecules, which were characterized by the p-polarized infrared reflection absorption spectroscopy (IRRAS). Furthermore, numerous steps along the ⟨110⟩ and ⟨11̅0⟩ directions and the resulting rectangular pits were observed by atomic force microscopy on the surface. The presence of these structures was also supported by the IRRAS.