Structural transformations at the surface of the decagonal quasicrystalAl70Co15Ni15

By using Auger electron spectroscopy and secondary-electron imaging, we show that, as a result of bombardment with 1.5-keV ${\mathrm{Ar}}^{+}$ ions, Al is preferentially sputtered and the surface structure of a decagonal ${\mathrm{Al}}_{70}{\mathrm{Co}}_{15}{\mathrm{Ni}}_{15}$ quasicrystal transforms to body-centered cubic. Annealing the sample at 700 K restores the Al concentration at the surface and, thereby, the quasicrystalline structure. Real-time observations establish the orientational relationship between the quasicrystalline and cubic surface structures, which we use to propose an atomic model of their interface.