Scanning tunneling microscopy study of the fivefold surface of icosahedral Al-Cu-Ru quasicrystal

We present the first report on real space images of the fivefold surface of icosahedral (i)-Al-Cu-Ru quasicrystal. Scanning tunneling microscopy images reveal that the atomic arrangement on the surface is basically equivalent to that of i-Al-Cu-Fe, an isostructure of i-Al-Cu-Ru. The stacking sequence of steps and the nature of step bunching are consistent with the inter-layer spacing rule, which we have previously proposed as a rule for the surface termination for the fivefold surface of Al-based icosahedral quasicrystals.