The reactivity and bonding of oxygen on the α-Cu17%Al(100) surface studied by UPS

Abstract

The reactivity and the bonding of oxygen on the α-Cu17%Al(100) alloy are investigated using ultraviolet photoelectron spectroscopy (UPS), and the results are compared with those of Cu(100). In the first stage of the reaction, oxygen reacts with the Al atoms on the alloy surface. Since there is no Al enrichment on the clean alloy surface, only a relatively small exposure of oxygen is required to saturate these sites. This oxygen does not penetrate into the alloy surface, but remains as an overlayer with the oxygen atoms chemisorbed at the Al sites. As a result of this surface surface oxidation, a second stage of reaction follows, in which more Al atoms segregate to the surface at a very slow rate and continue the reaction with oxygen. The slow migration rate of Al atoms, which is difficult to observe within the normal experimental duration, is the rate-limiting process of the second stage of the reaction. However, given enough time, Al enriches at the alloy surface in multilayer quantities, forming Al 2O 3.