He/Ar-atom scattering from molecular monolayers:C60/Pt(111) and graphene/Pt(111)

Abstract

Supersonic He and Ar atomic beam scattering fromC60 and graphene monolayers adsorbed on a Pt(111) surface are demonstrated in order toobtain detailed insight into a gas–molecule collision that has not been studied in detail sofar. The effective masses and phonon spectral densities of the monolayers seen by differentprojectiles are discussed based on classical models such as the hard cube model and therecently developed smooth surface model. Large effective masses are deduced for both themonolayers, suggesting collective effects of surface atoms in the single collision event. Theeffective Debye temperature of graphene was found to be similar to that reported in highlyoriented pyrolytic graphite (HOPG), indicating that the graphene is decoupled wellfrom the Pt substrate. A much smaller Debye–Waller factor was found for theC60 layer, probablyreflecting the strong C60–Pt(111) interaction.