Single element quasicrystalline monolayers were prepared by deposition of antimony and bismuth on the fivefold surface of icosahedral Al71.5Pd21Mn8.5 and the tenfold surface of decagonal Al71.8Ni14.8Co13.4. 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+/-0.2)x10(15) cm(-2) and (0.8+/-0.2)x10(15) cm(-2) on Al-Pd-Mn and Al-Ni-Co, respectively, correspond to roughly one adatom per Al atom of the quasicrystalline substrate surfaces.

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Scanning tunneling spectroscopy is used to study p-type Ge(111)c(8 2 ×) sur faces over the temperature range 7 to 61 K. Surface states arising from adatoms and rest-atoms are observed. With consideration of tip-induced band bending, a surface band gap of 1 0 5 0. . ± eV separating the bulk valence band from the surface adatom band is deduced. Peak positions of adatom states are located at energies of eV 02 0 09 0. . ± and eV 03 0 24 0. . ± above this gap. A spectral feature arising from inversion of the adatom state occupation is also identified. A solution of Poisson's equation for the tipsemiconductor system yields a value for the interband current in agreement with the observations, for an assumed tip radius of 100 nm. The rest-atom spectral peak, observed at eV 0. 1 ≈ below the valence band maximum, is observed to shift as a function of tunnel current. It is argued that nonequilibrium occupation of disorder-induced surface states produces this shift.

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Deviating from the common growth mode of molecular films of organic molecules where the adsorbates remain intact, we observe an essentially different growth behavior for metallocenes with a low temperature scanning tunneling microscope. Ferrocene molecules adsorb dissociatively and form a two layer structure. The top layer unit cell is composed of two tilted cyclopentadienyl (cp) rings, while the first layer consists of ferrocene molecules and cp-Fe complexes. Surprisingly a fourfold symmetry is observed for the top layer while the first layer displays threefold symmetry elements. It is this symmetry mismatch which induces an incommensurability between these layers in all except one surface direction. The top layer is weakly bonded and has an antiferromagnetic ground state as calculated by local spin density functional approximation.