Preparation and characterization of MgO surfaces by reflection electron microscopy.

We have employed several different methods to prepare (100) and (111) surfaces of MgO crystals. (100) surfaces prepared by simple cleaving give good reflection high energy electron diffraction (RHEED) patterns and surfaces with a high density of coarse steps. Chemical polishing of this surface results in a roughening of the topography whilst annealing in oxygen considerably smoothens the surfaces although they appear to be contaminated. Under certain conditions we find that the MgO crystals will cleave along the (111) plane. Both cleaved and mechanically polished (111) surfaces are atomically flat and reconstructed after oxygen annealing.