Raman Studies of Nano‐ and Ultra‐nanocrystalline Diamond Films Grown by Hot‐Filament CVD

A multi‐wavelength, visible‐Raman study of structurally different nanocrystalline diamond (NCD) films grown by means of hot‐filament (HF)CVD is presented. The Raman spectra are qualitatively and quantitatively analyzed by applying current interpretation models. It is demonstrated that specific properties of the diamond phase as well as the grain boundaries can be extracted from the Raman spectra. Hydrogenated amorphous carbon is detected in the film's grain boundaries and characterized regarding its hydrogen content, optical gap, and sp 3 content. The characteristic trans‐polyacetylene‐like signals are observed, and the behavior of the corresponding peaks studied in detail. The results are correlated with film properties such as grain size, morphology, roughness, and refractive index, as determined by atomic force microscopy (AFM), X‐ray diffraction (XRD), and ellipsometry.