He and Ar beam scatterings from bare and defect induced graphite surfaces

Abstract

The effect of the local electronic modification of the graphite surface on thegas–graphite interaction has been investigated by the molecular beam scatteringtechnique. The angular intensity distributions of He and Ar beams scatteredfrom pristine and defect induced graphite surfaces have been measured at varioussurface temperatures. From the He scattering results, the cross-section forthe He diffuse scattering per defect is estimated as being as much as 113 nm2.The origin of the extremely large cross-section is ascribed to the modulated electronic states ofgraphite around the defect based on the STM measurements, which is due to the local breaking of theπ conjugated system of graphite. From the Ar scattering results, the effectivemass of the graphite surface for the Ar collision has been estimated asM = 114 u, based on the analysis with the hard cube model. The new component appears inthe scattering distribution of Ar for the defect induced graphite surface. Thecomponent has a larger peak position angle than that for the pristine graphitesurface, indicating that the normal component of the translational energy of theAr atom was greatly lost by the collision at the electronically modified area ofgraphite.