Well-ordered ultra-thin Al2O3 films were grown on NiAl (1 1 0) surface by exposing the sample at various oxygen absorption temperatures ranging from 570 to 1100 K at dose rates 6.6 x 10(-5) and 6.6 x 10(-6) Pa. From the results of low-energy electron diffraction (LEED), Auger electron spectrometer (AES) and X-ray photon spectroscopy (XPS) observations, it was revealed that oxidation mechanism above 770 K is different from well-known two-step process. At high temperature, oxidation and crystallization occurred simultaneously while in two-step process oxidation and crystallization occurred one after another. At high-temperature oxidation well-ordered crystalline oxide can be formed by a single-step without annealing. Well-ordered Al2O3 layer with thickness over 1 nm was obtained in oxygen absorption temperature 1070 K and a dose rate 6.6 x 10(-6) Pa at 1200 L oxygen. (C) 2004 Elsevier B.V. All rights reserved.