XPS study of nitridation of diamond and graphite with a nitrogen ion beam

Diamond (CVD.) and graphite (HOPG) samples were nitrided at room temperature by irradiation with 300-700 eV N-2(+) ion beams. X-ray photoelectron spectra (XPS) were recorded in situ during the nitridation. The YPS spectra of Cls and N1s core levels are divided into three (A, B, C) and four (D, E, F, G) components, respectively. The A component at similar to 284.8 eV is assigned to the non-damaged substrate below the ion penetration depth. The B component at similar to 286.0 eV originates in the damaged phase and the sub-nitride phase (CNx: x < 1). The C component at similar to 287.3 eV is attributed to genuine nitrides such as C3N4. The broad N1s XPS peak at similar to 400 eV splits clearly into the D (similar to 398.4 eV) and F (similar to 401.2 eV) components upon annealing at 600 degreesC in vacuum. The splitting is caused by evaporation of the volatile E component (similar to 399.7 eV). The intensity of the D component was always comparable to that of the F component in both diamond and graphite cases. The origins of these components are discussed. The G component may be due to nitrogen trapped at defects. (C) 2001 Elsevier Science B.V. All rights reserved.