C60 adsorption on a dodecagonal oxide quasicrystal

Quasicrystalline surfaces are potential templates for highly ordered but aperiodic molecular self-assemblies. Here, we report on the adsorption of ${\mathrm{C}}_{60}$ molecules on a two-dimensional oxide quasicrystal (OQC) and its $\ensuremath{\sigma}$-phase approximant at room temperature and $150\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. The molecular films have been characterized by means of scanning tunneling microscopy and low-energy electron diffraction. A weak interaction of the molecules with the dodecagonal oxide template is found, resulting in a low desorption temperature of $510\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. For low temperatures specific adsorption sites within the tiling of the OQC and the $\ensuremath{\sigma}$-phase approximant have been identified as preferred nucleation sites. The narrow spacing between these sites introduces repulsive interaction between ${\mathrm{C}}_{60}$ molecules and restricts the epitaxial growth to small patches. At room temperature, ${\mathrm{C}}_{60}$ nucleates in hcp islands of almost arbitrary rotational orientation on the OQC. A slight orientational preference for hexagonal islands with a ${15}^{\ensuremath{\circ}}$ rotation against the OQC tiling is discussed as a consequence of the preferential adsorption on the quadratic tiles.