Assessment of spectroscopic methods for the characterisation of DLC films deposited by PECVD

Aim of the present work is to deposit and characterize a-C:H films by a range of spectroscopic methods in order to classify them according to their structural criteria: hydrogen and sp content. In order to meet this objective, the following approach was used. Carbon films within a large range of properties were synthesised by a special RF-ICP/CCP plasma source allowing to vary particle energies from a few electronvolts to keV on the one hand and chemical composition by mixing suitable precursor gases (methane, acetylene) with hydrogen on the other hand. Analytical approaches based on FTIR and Raman spectroscopy for film characterisation have been validated by consistency between them and by calibration in comparison to techniques (e.g. NRA for hydrogen and EELS for sp content) known to give reliable results without calibration but limited in applicability. The results obtained provide a means to confidently classify a-C:H materials with high spatial resolution, even on “3D”-samples, without destruction of the workpiece, and thus can contribute to quality assurance in industrial coating.