The formation of Al O -layers on Ni Al 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. q1999 Elsevier Science B.V. All rights reserved