Structure of Gd2O3 films epitaxially grown on GaAs(100) and GaN(0001) surfaces

Atomically thin films of Gd2O3 grow on GaAs(100) in the cubic alpha-Mn2O3 structure exposing the (110) surface. The film disorders upon brief sputtering with 1000 eV Ar+ ions for 10 s. Subsequent annealing of the sample at 700 K restores the crystalline structure, however, with fourfold symmetry. Core-level binding energy shifts show that the chemical states of all four components change upon sputtering and change further upon annealing. This observation is consistent with breaking and subsequent restoring of the chemical bonds at the Gd2O3/GaAs interface during surface processes until a new compound is formed. The Gd2O3 films grown on GaN(111) are stabilized in the high-temperature hexagonal phase exposing their sixfold symmetric surface. Secondary electron imaging patterns recorded during sequential sputtering reveal that there is a high degree of rotational alignment of crystallographic features at the Gd2O3/GaN interface. Copyright (C) 2002 John Wiley Sons, Ltd.