Epitaxial C60 films on CaF2 (111) grown by molecular beam deposition

Abstract

Epitaxial C60 films grown by molecular beam deposition onto CaF2(111) surfaces are investigated by reflection high-energy electron diffraction at deposition temperatures of 30–300 °C and coverages corresponding to average thicknesses of 1–50 nm. Over this entire temperature range, C60 forms an incommensurate overgrowth of stacked hexagonal layers exhibiting a characteristic nearest-neighbor spacing of 0.98 nm. Below 170 °C, unidirectional growth occurs in accordance with the crystallographic directions of the substrate. At higher deposition temperatures, however, two equivalent, rotated domain orientations are observed which are characterized by a significantly lower degree of lattice mismatch.