CHARACTERIZATION OF CLEAVED MGO(100) SURFACES

Cleaved MgO surfaces are characterized under ultra-high vacuum (UHV) c onditions, by means of atomic force microscopy (AFM) and X-ray photoel ectron spectroscopy (XPS). To obtain well-defined samples, MgO crystal s are cleaved under dry nitrogen, prior to being quickly inserted in U HV via a load-lock system. AFM images show 10 to 100 nm wide (100) ter races running over distances of microns. After either adsorption or co ntamination in UHV, cleaved MgO surfaces can be cleaned by heating sam ples at 1200 K under an oxygen pressure > 10(-3) Pa without inducing a ny visible change in the surface morphology. In contrast, the exposure to ambient air strongly affects these surfaces by irreversibly produc ing disordered similar to 10 X 10 nm(2) patches.