Epitaxial C films on CaF (111) grown by molecular beam deposition

Epitaxial C films grown by molecular beam deposition onto CaF(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, C 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.