| Epitaxial ZrC thin films were grown on Si (001), Si (111), and sapphire (0001) substrate by the pulsed laser deposition technique. It has been found that crystalline films could be grown only by using laser fluences higher than 6 J/cm2 and substrate temperatures in excess of 600 °C. For a fluence over 8 J/cm2 and a substrate temperature of 600∼700 °C, cubic ZrC films exhibiting a (001) texture were deposited under vacuum or low pressure C2H2 atmosphere. Under very low water vapor pressures (10-8∼10-9 Torr), high substrate temperatures (700∼750 °C), and high laser fluence (10 J/cm 2), highly textured ZrC films were deposited on single crystalline substrates. Pole figures investigation showed that films were epitaxial, with in-plane axis aligned with respect to those of the substrate. X-ray reflectivity, atomic force microscope, ellipsometry, and scanning electron microscopy confirmed that these films were smooth, with surface roughness values below 1.0 nm and mass densities around the stoichiometric ZrC tabulated value of 6.7 g/cm 3. X-ray photoelectron spectroscopy and Auger electron spectroscopy investigations showed that the surface of the films contained a significant amount of oxygen and Zr-O bonds, the outmost 1∼2 nm of the surface region being mainly ZrO2. However, after the removal of this surface contamination layer, low oxygen atomic concentration below 3 % were measured. Despite of the rather high levels of oxygen contamination, electrical resistivity measured by four probe measurement indicated that the deposited ZrC films were very conductive. The use of a low C2H2 pressure atmosphere during deposition had a small beneficial effect on crystallinity and stoichiometry of the films. Nanoindentation measurements showed higher values of the hardness for higher crystallinity. For the highest crystalline quality, (111) ZrC films deposited on sapphire, values over 450 GPa for the elastic modulus and ∼31 GPa for the hardness were measured. |
