The thermal stability of amorphous hard carbon films produced by cathodic arc deposition was studied by near edge x-ray absorption fine structure (NEXAFS) spectroscopy, Raman spectroscopy, and nanoindentation evaluation. Pure carbon films of up to 85&percent;sp3content were deposited using a pulsed biasing technique and annealed in ultrahigh vacuum up to 850 °C. NEXAFS spectra show no change in the film properties up to 700 °C, and a modification of the spectra for 800 and 850 °C, which indicate graphitization. Raman spectra show only a very slight change up to 850 °C. The nanoindentation data show no change in hardness and elastic modulus with annealing up to 850 °C. The study demonstrates the high thermal stability of the films. The difference in the NEXAFS and the Raman and nanoindentation results can be attributed to the surface sensitivity of NEXAFS in comparison to the more bulk sensitivity of Raman spectroscopy and nanoindentation. ©1997 American Institute of Physics.