C 1s binding-energy shift of pyrolytic graphite bombarded by keV-deuterium ions.

Abstract

As a basic study of plasma-wall interactions, chemical state of graphite basal face after deuterium bombardment are studied by means of X-ray photoelectron spectroscopy. As the ftuence of deuterium ions with energy of 1 or 4 keY is increased from lOu to 10 18 ions/cm 2 , the C ls line is observed to shift towards the lower binding energy at first, down to the minimum by about 0.2 eV and then towards the higher energy up to an asymptotic value of about 0.2 eV higher than the initial position. The first negative shift is due to lattice displacement at the target surface, and the subsequent positive shift is due to the deuterium trapping at the graphite surface. The fluence dependence of the observed C ls shift is explained by a simple saturation model.

Electron spectroscopy measurements on hydrogen implanted graphite and comparison to amorphous hydrogenated carbon films (a-C:H)

“…XPS C1s core level spectra of HOPG, HOPG : H and a-C : H the same electron excitation energy, no conclusion about the peak intensity can be drawn. The Cls measurements are in good agreement with results obtained in earlier studies on deuterium implanted graphite [9,10]. However, the interpretation of the Cls shift drawn by Gotoh et al [10] has to be reconsidered.…”

“…The Cls measurements are in good agreement with results obtained in earlier studies on deuterium implanted graphite [9,10]. However, the interpretation of the Cls shift drawn by Gotoh et al [10] has to be reconsidered. In their work, the Cls binding energy is expressed by a sum of two analytical functions, of which one function was assumed to be proportional to the damage density and the other proportional to the hydrogen trapping density.…”

“…5 for comparison to HOPG:H. As in the case of HOPG:H, the Cls peak of a-C:H is strongly broadened. Note the close agreement in the FWHM and line shape of the Cls signal between a-C:H and HOPG :H. Gotoh et al [10] interpreted the larger Cls FWHM after hydrogen bombardment of graphite by the admixture of tetrahedrally coordinated carbon atoms in the implanted overlayer. Our direct comparison between HOPG:H and a-C:H, which consists of about 70% D. Ugolini et al…”

“…A few X-ray photoelectron spectroscopy (XPS) studies of hydrogen-implanted graphite already exist [9,10]. However, the present combination of ultraviolet photoelectron spectroscopy (UPS), electron energy loss spectroscopy (EELS) and XPS yields new structural information on hydrogen-implanted graphite.…”

Energetic deuterium and helium irradiation effects on chemical structure of CVD diamond

“…The energy shift could be attributed to irradiation damage such as lattice displacements [8,9]. The increase of the FWHM was due to the presence of more than one bonding phase.…”