The formation of Al2O3-layers on Ni3Al(111)

We have investigated the formation of thin oxide films grown by oxidation of a Ni3Al(111) surface using scanning tunneling microscopy (STM). Oxygen was adsorbed at 300 K, 600 K, and 1000 K and subsequently annealed at 1000 K for several minutes. The distribution of the oxide islands at step edges and on terraces shows a strong dependence of the adsorption temperature. At 300 K and 600 K, oxide islands at step edges and on terraces are found, whereas at 1000 K, islands grow exclusively at step edges. This can be explained by the limited diffusion and surface segregation of Al at temperatures below 900 K. (C) 1999 Elsevier Science B.V. All rights reserved.