Temperature-dependent interaction of C60 with Ge(1 1 1)-c(2 × 8)

We report photoemission and low energy electron diffraction (LEED) data of a C60 multilayer adsorbed on Ge(1 1 1)-c(2×8) surface, as a function of annealing temperature. Remarkable changes take place in the valence band (VB) as the temperature is increased. Three phases are revealed, with different LEED patterns, coverages and molecular distance, including a ‘bulk-like’ C60 hexagonal single layer, not observed so far, the 3√3×3√3R30° and √13×√13R14° phases already known from literature. The ultra-violet VB spectra show strong similarities with C60 adsorbed on Si surfaces, with the splitting of the C60 highest occupied molecular orbital (HOMO) derived bands into two peaks, due to the C60 bonding with the substrate. The bond is activated by the temperature and implies molecular deformation. At ∼700 °C the C60 features disappear and core level photoemission spectra indicate carbon desorption or interdiffusion into the substrate.