Density, sp3 content and internal layering of DLC films by X-ray reflectivity and electron energy loss spectroscopy

A variety of hydrogenated and non-hydrogenated amorphous carbon thin films have been characterised by means of grazing-incidence X-ray reflectivity (XRR) to give information about their density, thickness, surface roughness and layering. We used XRR to validate the density of ta-C, ta-C:H and a-C:H films derived from the valence plasmon in electron energy loss spectroscopy measurements, up to 3.26 and 2.39g/cm(3) for ta-C and ta-C:H, respectively. By comparing XRR and electron energy loss spectroscopy (EELS) data, we have been able for the first time to fit a common electron effective mass of m*/m(e) = 0.87 for all amorphous carbons and diamond, validating the 'quasi-free' electron approach to density from valence plasmon energy. While hydrogenated films are found to be substantially uniform in density across the him, ta-C films grown by the filtered cathodic vacuum are (FCVA) show a multilayer structure. However, ta-C films grown with an S-bend filter show a high uniformity and only a slight dependence on the substrate bias of both sp(3) and layering. (C) 2000 Elsevier Science S.A. All rights reserved.