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

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