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In this study, we have employed high-resolution x-ray photo-absorption (NEXAFS) and reflectivity (XRR)spectroscopies to study the role of hydrogen and Si-addition on the electronic strcuture of tetrahedral amorphous carbon (ta-C) films. The ta-C films are deposited using Filtered Cathodic Vacuum Arc (FCVA) system under varying tetramethylsilane (Si(CH3)4; TMS) precursor gas pressure. The relative change in the area ratio of resonance absorption peaks of NEXAFS spectra, located respectively at 285.3eV and 289eV, has been used to determine the sp2-bonding in the films. The C K-edge NEXAFS spectra indicate that the sp2/sp3 hybridization ratio increases as the amount of tetramethylsilane precursor increases during deposition, which suggest that TMS-addition enhances sp2 and reduce sp3-bonding configurations. Also, x-ray reflectivity, XRR, measurements have indicated that the incorporation process has affected the connectivity and hardness of the network. In-situ rapid thermal annealing, RTA, has confirmed the graphitization process caused by Si- and hydrogen-additions. It is believed that the evolution of hydrogen during thermal annealing process, as revealed by heavy-ion elastic recoil detection (ERD) measurements, is responsible for the observed thermal instability. Angular dependent NEXAFS spectra of as-grown ta-C:Si:H films at the C K-edge revealed significant dopant induced local ordering in π*C=C and σ*C-H orbitals. The π*C=C resonance intensity decreases from normal to glancing incidence, while the σ*C-H exhibits an opposite behaviour. These angle-dependent trends suggest that the π *C=C orbitals lie parallel to the Si substrate surface. |