Amorphization of carbon materials studied by X-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy have been applied to investigate amorphization processes by ion irradiation for various carbons, including highly oriented pyrolytic graphite (HOPG), isotropic graphite, glassy carbon (GC) and C-60. It is found that the asymmetry of the XPS C ls line increases as the irradiation dose increases. The origin of the asymmetry appeared on the C ls line is discussed. We conclude that the asymmetry of the C ls line does not relate to the increase in the size of a graphitic layer, but relates to structural disorders, such as a bond angle disorder. (c) 2005 Elsevier B.V. All rights reserved.