Elemental steps in the growth of thin beta-Ca2O3 films on CoGa(100)

The oxidation of CoGa(1 0 0) at 700 K was studied by means of high resoluti on electron energy loss spectroscopy (EELS), scanning tunneling microscopy, low energy electron diffraction and Auger electron spectroscopy (AES). At 700 K, thin well-ordered beta -Ga2O3 films grow on CoGa(1 0 0). The EEL spe ctrum of the Ga-oxide films exhibit Fuchs-Kliewer phonons at 305, 455, 645, and 785 cm(-1). For low oxygen exposure (<0.2 L), the growth of oxide-isla nds starts at step edges and on defects. The oxide films have the shape of long, rectangular islands and are oriented in the [1 0 0] and [0 1 0] direc tions of the substrate. For higher oxygen exposure, islands of <beta>-Ga2O3 are found also on the terraces. After an exposure of 200 L O-2 at 700 K, t he CoGa(1 0 0) surface is homogeneously covered with a thin film of beta -G a2O3. (C) 2001 Elsevier Science B.V. All rights reserved.