C₅₈on HOPG: Soft-landing adsorption and thermal desorption

Abstract

Electron-impact induced dissociation/ionization of C60 molecules was used to produce an intense beam of C58+ ions. This was directed towards a HOPG (highly oriented pyrolytic graphite) substrate under nominally perpendicular impact conditions in order to generate deposits by soft-landing (kinetic energy < 0.1 eV atom−1). Deposited C58 molecules could subsequently be thermally desorbed intactly. Thermal desorption mass spectra of the deposits exhibit only C58. Surface deposited C58 can react with background gases to generate hydride derivatives C58Hn which are also desorbable. The apparent desorption energy of C58 and C58Hn molecules from the HOPG surface varies with increasing adsorbate coverage from 2 ± 0.1 to 2.2 ± 0.1 eV as determined by a Redhead analysis. These values are 0.7 ± 0.1 eV larger than found for C60 desorbed from the same substrate.