Decagonal epilayers on the icosahedral quasicrystal Al70Pd20Mn10

The pentagonal surface of the icosahedral quasicrystal Al70Pd20Mn10 becomes decagonal upon sputtering with Ar+ ions at elevated temperatures. This dec agonal surface has a vastly different chemical composition (Al22Pd56Mn22) t han bulk decagonal quasicrystals (Al70Pd10Mn20) and is coherent with the ic osahedral substrate across the entire macroscopic sample. The transformatio n of this surface back to the original icosahedral structure and compositio n during annealing is followed in real space and in real time with secondar y-electron imaging. The structural changes during this transformation are d iscussed in light of current models of decagonal and icosahedral quasicryst als.