PREPARATION AND CHARACTERIZATION OF MGO(100) SURFACES

The preparation of crystalline magnesium oxide surfaces by means of me chanical polishing, acid etching, oxidative annealing and vacuum annea ling has been studied on an atomic scale using low energy electron dif fraction (LEED) and ultrahigh vacuum (UHV) atomic force microscopy (AF M). Mechanical polishing results in a microscopically smooth and an at omically disordered surface. Although acid etching of the magnesium ox ide surface results in LEED patterns indicating a crystalline nature, AFM characterization of these surfaces reveals that surface layers are removed in an anisotropic fashion resulting in a surface roughness on the order of 100 Angstrom (which is not probed by the LEED studies). Annealing this same surface in vacuum only modestly reduces the surfac e roughness while high temperature anneals of an acid etched surface i n a 1 atm oxygen environment produces a well ordered surface character ized by 1000 Angstrom terraces separated by single and double layer st ep heights. Further annealing these terraced surfaces to 1000 degrees C under vacuum produced well-ordered and crystallographic surfaces on an atomic scale. Topographic images of the MgO(100) surface obtained u nder UHV conditions reveal rows of oxygen atoms oriented in a [110] di rection with a spacing of 3.0 Angstrom and indicate that this surface preparation results in an unreconstructed, bulk termination of the roc k salt structure. (C) 1997 Elsevier Science B.V.