Composition, structure and mechanical property analysis of DC sputtered C-Ni and CNx-Ni nano-composite layers

Carbon-nickel (C-Ni) and carbon-nitride-nickel (CNx-Ni) films were deposited onto native SiO2 covered Si substrates by DC magnetron sputtering from a graphite-nickel composite target using Ar or N-2 for sputtering at about 2.6 Pa. The substrate temperature varied between 25 and 800degreesC. The structure, composition and mechanical properties of C-Ni and CNx-Ni thin layers (200-300 nn) have been investigated by high-resolution transmission electron microscopy (HRTEM), XPS, nano-indentation and nano-scratch techniques. The layers were predominantly crystalline irrespective of their deposition conditions. At low deposition temperature, up to 200degreesC, the columnar crystallites were identified as hexagonal Ni3C, separated by narrow 'walls' of amorphous carbon. At substrate temperatures above 400degreesC, however, a graphitic multilayer arrangement of the carbon matrix was developed around the nano-crystalline cubic nickel-nickel carbide islands. The mechanical properties of the films varied also significantly with the deposition temperature. The highest nano-hardness of about 14 GPa was measured for the film grown at 200degreesC, while lower values (2-4 GPa) were obtained for high-temperature films. High hardness values were related to the presence of Ni3C. The lowest friction coefficients were obtained for films containing high amounts of multi-layered graphite-like carbon developed at intermediate deposition temperatures. Copyright (C) 2004 John Wiley Sons, Ltd.