Abstract
Hot filament and microwave plasma CVD nanocrystalline diamond films are analysed by visible and ultra-violet excitation source Raman spectroscopy. The analysis of the shape and relative intensity of the different Raman features due to the sp2 phases, i.e. the sp2 1550 cm-1 G band attributed to C=C sp2 bond stretching mode, the D band (collective breathing mode of aromatic rings) and the shoulder observed at about 1150 cm-1 (assigned to transpolyacetylene segments) gives some information on the local structure of the sp2 phases. The surface of the samples is analysed by X-ray Photoelectron Spectroscopy (XPS). The evolution of the sp2 phases is analysed at the surface and in the bulk when the diamond films are submitted to thermal annealing under ultra-high vacuum or acidic surface oxidation. The decomposition of the C1s peak evidences graphitic phases attributed to the high density of grain boundaries.