Evaluation of the sp2/sp3 ratio in amorphous carbon structure by XPS and XAES

A comparison among XPS and XAES spectra features of graphite (sp 2 bonding), diamond (sp 3 bonding), amorphous carbon (i-C) and several hydrogenated amorphous carbon samples (i-C:H) has been carried out. XAES derivative spectra of graphite, i-C and i-C:H samples show a fine structure (275–280 eV) which is assigned to KVV transitions involving pπ electrons. An estimate of the sp 2 /sp 3 ratio on the basis of the presence of such structures in the spectra has been attempted. Values of the sp 2 /sp 3 ratio between 0.5 and 1.5 have been found for hydrogenated samples, whereas for amorphous carbon a value of 3 has been obtained.