We have developed a process for making thick, stress-free, amorphous-tetrahedrally bonded carbon(a-tC)films with hardness and stiffness near that of diamond. Using pulsed-laser deposition, thina-tCfilms (0.1–0.2 &mgr;m) were deposited at room temperature. The intrinsic stress in these films (6–8 GPa) was relieved by a short (2 min) anneal at 600 °C. Raman and electron energy-loss spectra from single-layer annealed specimens show only subtle changes from as-grown films. Subsequent deposition and annealing steps were used to build up thick layers. Films up to 1.2 &mgr;m thick have been grown that are adherent to the substrate and have low residual compressive stress(<0.2 GPa).The values of hardness and modulus determined directly from an Oliver–Pharr analysis of nanoindentation experimental data were 80.2 and 552 GPa, respectively. We used finite-element modeling of the experimental nanoindentation curves to separate the “intrinsic” film response from the measured substrate/film response. We found a hardness of 88 GPa and Young’s modulus of 1100 GPa. From these fits, a lower bound on the compressive yield stress of diamond(∼100 GPa)was determined. ©1997 American Institute of Physics.