EVIDENCE FOR A CLUSTER-BASED STRUCTURE OF ALPDMN SINGLE QUASI-CRYSTALS

For the first time quasicrystal surfaces produced by in situ cleavage in ultrahigh Vacuum have been investigated by scanning tunneling micro scopy. Twofold and fivefold surfaces of icosahedral AlPdMn single quas icrystals have been studied. The surfaces were found to be rough. Thei r structure is determined by cluster aggregates formed on the basis of an elementary cluster whose contrast behavior and diameter of about 1 nm point to the Mackay-type cluster. Crack propagation occurs along z ones of lower strength between clusters. This supports the cluster app roach to quasicrystal structure.