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We investigated the composition of decagonal Al-Co-Cu surface by Auger electron spectroscopy (AES) and low-energy ion scattering (LEIS). The surface composition after annealing was Al richer and Co poorer compared to that after sputtering or bulk composition. Two types of the characteristic clusters were observed by scanning tunneling microscopy (STM) and no bias voltage dependence of the image was observed. On the other hand, scanning tunneling spectroscopy revealed a subtle difference of local density of states in unoccupied states between different sites. Structural optimization using ab initio calculations based on density functional theory (DFT) was performed on several compositional models, which are based on the W-(AlCoNi) bulk model. The surface structures of two types of the characteristic clusters were determined by comparison of the STM image and the simulated image of the structures obtained by DFT. The topmost layer was composed of Al and Cu atoms, and the compositional ratio was consistent with the AES and LEIS results.

We have grown 22-ML-thick Fe films on a Cu(100) single crystal. The films were stabilized in the face-centered-cubic (fcc) $\ensuremath{\gamma}$ phase by adsorption of carbon monoxide during growth, preventing the transformation to the body-centered-cubic (bcc) $\ensuremath{\alpha}$ phase. A structural transformation of these films from fcc to bcc can be induced by ${\text{Ar}}^{+}$ ion irradiation. Scanning-tunneling microscopy images show the nucleation of bcc crystallites, which grow with increasing ${\text{Ar}}^{+}$ ion dose and eventually result in complete transformation of the film to bcc. Surface magneto-optic Kerr effect measurements confirm the transformation of the Fe film from paramagnetic (fcc) to ferromagnetic (bcc) with an in-plane easy axis. The transformation can also be observed by low-energy electron diffraction. We find only very few nucleation sites of the bcc phase and argue that nucleation of the bcc phase happens under special circumstances during resolidification of the molten iron in the thermal spike after ion impact. Intermixing with the Cu substrate impedes the transformation. We also demonstrate the transformation of films coated with Au to protect them from oxidation at ambient conditions.