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

Abstract

The oxidation of ${\mathrm{Ni}}_{\mathrm{3}}\mathrm{Al(111)}$ 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 Moiré structure, which is unrotated with respect to the substrate. Oxidation at 1050 K leads to highly ordered ${\mathrm{Al}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ 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 et 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.