Ultraviolet and visible Raman spectroscopy characterization of chemical vapor deposition diamond films

Polycrystalline diamond films with different grain sizes (10 nm, 100 nm and 5 μm) were prepared by hot-filament chemical vapor deposition (HFCVD). The diamond films have been studied using ultraviolet (UV, 244 nm), visible (Vis, 514 nm) and (Vis, 633 nm), near-infrared, micro-Raman scattering. The fluorescence in the excited diamond film is found to change considerably with the incident photon energy. The scattering intensity of amorphous sp2-bonded carbon compared to the strength of the 1331 cm−1 Raman line from sp3-bonded diamond is found to vary considerably as functions of the grain size of diamond film and the incident photon energy. Possible models for the structures of amorphous sp2-bonded carbon and sp3-bonded diamond phases are discussed on the basis of the present Raman data. It is shown that UV Raman spectroscopy has provided significantly greater information than visible Raman spectroscopy in characterizing diamond phases.