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The oxidation of Ni 3 Al͑111͒ 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 Al 2 O 3 thin films that exist in two rotational domains. In conjunction with previous measurements ͓Rosenhahn et al., Appl. Surf. Sci. 142, 169 ͑1999͒; Surf. Sci. 433-435, 705 ͑1999͒; C. Becker et al., J. Vac. Sci. Technol. A 16, 1000 ͑1998͔͒ it can be clearly be seen that the temperature strongly controls the chemical composition and the structure of the oxides.