Electron-stimulated reaction of C60 with a model etching gas, SF6

Abstract

High-resolution electron energy loss spectroscopy has been used to characterize changes induced in C60 films due to electron-stimulated reaction with SF6, a standard etching gas. A monolayer of SF6 was adsorbed at low temperature on 4 monolayer thick C60 films grown on Au(110). The C60 vibrational modes and SF6 vibrations observed were essentially unshifted from the pristine solid state and gas phase values, respectively, indicating a van der Waals-type interaction between SF6 and C60. These surfaces were subsequently irradiated with electrons of energy between 15 and 230 eV, stimulating a reaction between C60 and the adsorbed SF6. At low electron beam energy and electron dose (E=15 eV, 1.5×10−3 C cm−2), the electron-stimulated reaction of SF6 with C60 induces some disorder within the films, and subtle changes are observed in the vibrational spectra. At higher beam energy and electron dose (E=230 eV, 4.7×10−3 C cm−2), significant changes occur in the films as demonstrated by the appearance of strong disorder. The resulting material appears to have a graphite-like local structure. Several new vibrations are observed and may be due to the formation of graphitic sheets.