REM and REELS identifications of atomic terminations at α-alumina (01̄1) surface

Reflection electron microscopy (REM), reflection high energy electron diffraction (RHEED) and reflection electron energy-loss spectroscopy (REELS) have been combined to investigate the atomic structures at a α-alumina (01̄1) surface. The α-alumina (01̄1) shows light and dark regions which are interpreted as arising from termination of the structure by O-rich and Al-rich layers. It is the reactions of these different top layers with the atmosphere that are considered to give quite different contrast domains in the REM images. The surface domains with O-rich termination are found to be flat and create strong reflection intensity. The surface regions terminated by Al-rich layers are found to be rough and easily form surface oxides with the adsorbed oxygen from air. The structure modulation in a surface monolayer can significantly affect the excitation property of the surface and reduce the main travelling distance of the electrons along the surface. It is demonstrated that the combined techniques of REM, RHEED and REELS are useful tools for studying the chemical reactions between surface monolayers with gases.