Oxidation of Ni3Al(111) at 600, 800, and 1050 K investigated by scanning tunneling microscopy

The oxidation of Ni3Al(111) at 600, 800, and 1050 K was investigated using scanning tunneling microscopy. Exposing the alloy crystal to oxygen at 600 K results in triangular shaped oxidic nuclei at low coverage. At higher coverage a rather disordered oxide layer can be observed. At 800 K, highly ordered O/Al single layer islands with a triangular shape are formed throughout the coverage range. The islands show a Moire structure, which is unrotated with respect to the substrate. Oxidation at 1050 K leads to highly ordered Al2O3 thin films that exist in two rotational domains. In conjunction with previous measurements [Rosenhahn et al., Appl. Surf. Sci. 142, 169 (1999); Surf. Sci. 433-435, 705 (1999); C. Becker ct al., J. Vac. Sci. Technol. A 16, 1000 (1998)] it can be clearly be seen that the temperature strongly controls the chemical composition and the structure of the oxides. (C) 2000 American Vacuum Society. [S0734-2101(00)02904-3].