Evidence for a two-step evolution of the surface structure during heat treatment of cleaved icosahedral Al-Pd-Mn single quasicrystals

A two-step evolution of the surface structure of in situ cleaved Czochralsk i-grown icosahedral Al-Pd-Mn single quasicrystals during heat treatment is found by scanning electron and scanning tunneling microscopies. At temperat ures above 420 degrees C the surface becomes rough in certain areas, while in other areas the cluster-based structure of the cleavage surface remains essentially unchanged. Above 550 to 600 degrees C the rough surface areas e xhibit larger faceted holes and the cluster-based surface structure reorder s. Possible explanations of the two-step evolution are discussed. (C) 1999 Published by Elsevier Science B.V. All rights reserved.