Investigation of optical properties of a-C:H films deposited from acetylene using direct ion beam deposition method

The present work provides results for amorphous hydrogenated carbon (a-C:H) films deposited by a direct ion beam deposition method. Acetylene (C2H2) precursors and their mixture with hydrogen (H2) were used. The films were characterized by Raman spectroscopy (RS) and ellipsometry measurements. RS indicates an increase of sp3/sp2 bonding ratio and disorder in graphite clusters with increasing hydrogen content (from 0 to 50% for acetylene precursor) in the deposition of gas mixture. The opposite trend is observed when the hydrogen concentration exceeds 50% (for acetylene). The ellipsometric technique was used to reveal the optical constants of a-C:H films from the optical response of the complex system in the UV-VIS-NIR spectral range 0.5-5.0 eV. In the analysis of the optical response, the models of effective film and a multi-layer stack were used for a-C:H films.