Nanocrystalline growth and diagnostics of TiC and TiB2 hard coatings by pulsed laser deposition

Nanocrystalline coatings of TiC and TiB2 were grown by pulsed laser deposit ion on Si(100) and on X155 steel at low substrate temperatures ranging from 40 degrees C to 650 degrees C. A pulsed KrF excimer laser was used with th e deposition chamber at a base pressure of 10(-6) mbar. The morphology and structure of the films, studied with SEM, XRD, and TEM, showed that nanocry stalline films with a fine morphology of TiC and TiB2 were deposited with a grain size of 10 nm-70 nm at all substrate temperatures. The growth of the polycrystalline coatings possessed a columnar morphology with a [100] pref erred orientation. The hardness of the coatings was determined to be 40 GPa and the elastic modulus, 240 GPa. The composition and the kinetics of the plume produced during the pulsed laser deposition of TiC and TiB2 was studi ed under film growth conditions. The mass analysis of ions of the ejected m aterial was performed by time-of-flight mass spectroscopy (TOF-MS) and show ed the presence of Ti+ and C+ during TiC ablation and B+, B-2(+), and Ti+ d uring TiB2 ablation. The kinetic energies (KE) of the ions depended on the laser fluence which was between 0.5 eV and 340 eV. The kinetic energy and t he evolution of the plasma was studied with a streak camera. The velocity o f the plasma was of the order of 10(6) cm/sec and was linearly dependent on the energy fluence of the laser. The emission spectroscopy of the plasma p lume confirmed the atomic neutral and single excited species of Ti. These r esults show that coating growth basically occurs by the recombination of th e ionic species at the surface of the substrate.