Formation of an ordered oxide on the CoGa(100) surface by room temperatureoxidation and annealing

The preparation of an ordered GaO3 oxide on the GoGa(1 0 0) surface by expo sing the surface to oxygen at room temperature and subsequent annealing has been studied by thermal energy helium atom scattering and Auger electron s pectroscopy. During room temperature oxidation a disordered Ga2O3 layer for ms. The oxidation process is studied with lie scattering and the results ar e compared with previously reported scanning tunneling microscopy investiga tions. Upon annealing, it is found that ordering of the oxide layer proceed s very slowly. Even at a temperature of 800 K, 50 K below the temperature a t which the oxide decomposes and disappears from the surface, the ordering process is not yet completed after 1000 s. It is concluded that a smooth ox ide film can be prepared by room temperature exposure to oxygen and anneali ng at temperatures just below decomposition temperature of the oxide (850 K ) which is very uniform with respect to thickness. However, the amount of o xygen adsorbing at 300 K is not sufficient to produce a continuous film. Ab out 10-15% of the surface is not covered by the oxide after this preparatio n method. To prepare a continuous oxide layer several cycles of room temper ature oxidation and annealing seem necessary. (C) 2001 Elsevier Science B.V . All rights reserved.