Quasicrystalline Epitaxial Single Element Monolayers on Icosahedral Al-Pd-Mn and Decagonal Al-Ni-Co Quasicrystal Surfaces

Single element quasicrystalline monolayers were prepared by deposition of antimony and bismuth on the fivefold surface of icosahedral ${\mathrm{A}\mathrm{l}}_{71.5}{\mathrm{P}\mathrm{d}}_{21}{\mathrm{M}\mathrm{n}}_{8.5}$ and the tenfold surface of decagonal ${\mathrm{A}\mathrm{l}}_{71.8}{\mathrm{N}\mathrm{i}}_{14.8}{\mathrm{C}\mathrm{o}}_{13.4}$. Elastic helium atom scattering and low energy electron diffraction of the monolayers show Bragg peaks at the bulk derived positions of the clean surfaces, revealing highly ordered quasicrystalline epitaxial films. Their adatom densities of $(0.9\pm 0.2)\times {10}^{15}{\mathrm{c}\mathrm{m}}^{-2}$ and $(0.8\pm 0.2)\times {10}^{15}{\mathrm{c}\mathrm{m}}^{-2}$ on Al-Pd-Mn and Al-Ni-Co, respectively, correspond to roughly one adatom per Al atom of the quasicrystalline substrate surfaces.

Figure 1

Evolution of the intensity of the specular He atom beam for Bi deposition on (a) GaAs(110), (b) the fivefold surface of Al-Pd-Mn, and (c) the tenfold surface of Al-Ni-Co. The coverages in the first layer ${\Theta }_1$ determined by the model calculations (thin curves, see text) are shown on the horizontal axis. ${\Theta }_{\mathrm{M}\mathrm{L}}$ is the resulting coverage of the completed monolayer. Sample temperatures were 20 °C, 150 °C, and $-50°\mathrm{C}$, respectively. The beam energy was 15 meV.

Figure 2

LEED images from the fivefold Al-Pd-Mn surface with electron energy of 63 eV: (a) clean surface, (b) Sb monolayer, and (c) Bi monolayer. Although the patterns from the monolayers (b),(c) appear tenfold, different electron energies confirm a fivefold symmetry. Indexing follows Ref. 27.

Figure 3

He atom diffraction from the clean surface and the Sb and Bi monolayers on the fivefold surface of Al-Pd-Mn (a),(b) and the tenfold surface of Al-Ni-Co (c),(d) with 15 and 22 meV kinetic energy, respectively. In each panel the spectra from top to bottom are of the clean surface (scale on the left-hand side), Bi monolayer (scale on the right), and Sb monolayer (scale on the left). Note the logarithmic scale. Indexing as in Fig. 2 and Ref. 27.