Neutron-scattering study of methane bilayer and trilayer films on graphite

The results of a neutron-diffraction study of the multilayer growth properties of methane on a graphite substrate are presented. The experiments, performed over an extended temperature range, follow the layering behavior from the submonolayer region to approximately three layers. The completed monolayer film is found to be overcompressed with respect to the bulk value. A stacking sequence and lattice parameter close to that of the bulk solid are found near three layers. The bilayer region, however, is characterized by a diffraction pattern which is not consistent with two layers in perfect registry with one another.