Growth mode of multilayer methane on graphite at low temperatures

Abstract

The growth process of multilayer methane on graphite was studied by a.c. heat-capacity technique in the temperature range 4–40 K. The heat-capacity anomalies related to orientational-ordering transitions show gradual change with increasing coverage towards bulk-like behaviour. This result is consistent with the conclusion that methane grows layer by layer on graphite surface for temperatures > 20 K. Another heat-capacity anomaly, unrelated to orientational-ordering transitions, was observed near 11 K for methane film with coverages higher than two layers. We suggest this anomaly is probably related to a structural transition in the multilayer film, possibly due to a wetting transition.