QUASI-CRYSTALLINE STRUCTURE OF ICOSAHEDRAL AL68PD23MN9 RESOLVED BY SCANNING-TUNNELING-MICROSCOPY

For the first time die surface structure of an icosahedral quasicrysta l could be resolved in direct space by scanning tunneling microscopy. The surface was found to form terraces with their normals being parall el to a fivefold axis. On the terraces fivefold stars and pentagonal h oles were observed. Both the step heights and the distances between pe ntagonal holes obey Fibonacci sequences. The distribution of the holes locally resembles a Penrose tiling and is correlated up to long dista nces indicating a quasiperiodic order. A simple model yields an autoco rrelation function very similar to the experiment.