Study of the response of the fivefold i-AlPdMn surface to different temperature treatments

Chemical and structural surface evolution of an icosahedral AlPdMn sample was systematically studied after ultrahigh vacuum surface preparations based on ion sputtering followed by annealing. Depending on the annealing temperature we observed different surface phases. For annealing temperatures below 700 K a thin crystalline surface was formed on the quasi-crystal bulk. For annealing temperatures between 700 and 900 K we found a quasi-crystalline surface that can be interpreted as a bulk-terminated one. For high temperature annealing (>950 K) the surface observed at high temperature was different to that obtained after cooling to room temperature. The cooled sample exhibited again a crystalline thick layer. In order to study the eventual influence of the original quasi-periodic structure on the evaporation, we further investigated the high temperature annealing regime from 950 to 1050 K, where we observed the initial stage of a preferential evaporation of manganese atoms. Finally, we obtained direct experimental evidence for a spontaneous deoxidation of the quasi-crystal. (C) 2000 Published by Elsevier Science B.V. All rights reserved.