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Tetrahedral amorphous carbon (ta-C) films have attracted a research interest due to their superior properties over hydrogenated amorphous carbon films. These types of films have a major drawback, which is the large residual stress. This high-level of residual stress has restricted the growth of thick films (>150 nm) and limited their use in particular applications such as diffusion barrier coatings. In this work, we report an effective method of reducing the high-residual stress, while retaining the diamond-like properties (high sp3 hybridization fraction) of filtered cathodic arc tetrahedral amorphous carbon (ta-C) films. The structural stability during post-deposition rapid thermal annealing, RTA, process has been investigated using spectroscopic techniques such as near-edge x-ray absorption fine structure, NEXAFS, x-ray reflectometry, XRR, spectroscopic ellipsometry, SE, and ultraviolet (UV)-Raman spectroscopy. The peaks intensity ratio, π*285.5 / σ*289, of the C K-photo-absorption spectra has been used to determine the relative quantity of sp2 and sp3 bonding in the annealed films. The *C=C for the as-deposited ta-C film was much smaller than that of graphite, showing that the deposited film posses high sp3 content. However, as the annealing temperature is increasing beyond 800°C, the intensity of the π*C=C peak is developing with a slight peak-shift to the value of that corresponding to graphite sample. The increase in both intensity and width of the π*C=C indicates a progressive graphitization of the ta-C sample with annealing. The widening of the π* resonance peak indicates the initiation and development of new π* states which lay at different energies in comparison with those of non-annealed films. The higher energy of these new states suggests that they should be associated to π bonds in the graphitized carbon. On the other hand, a surface profiler revealed that a complete stress-relief in the ta-C films was achieved at 700-800°C. Additionally, the optical band gap, E opt, slightly increased from 2.2 eV at RT to 2.4 eV at 800°C. This result demonstrates the possibility of enhancing the optical properties of ta-C films by a RTA strategy. |