Physical properties of a-C: N films produced by ion beam assisted deposition
- PDF / 1,542,729 Bytes
- 10 Pages / 576 x 792 pts Page_size
- 42 Downloads / 232 Views
Bernard Andre CEREM, Centre d'Etudes Nucleates de Grenoble, BP85X 38041 Grenoble Cedex, France
A. van Veen, P. E. Mijnarends, H. Schut, and F. Labohm IRI, Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands
Hugh Dunlop Pechiney CRV, BP 27 38040 Voreppe, France
Marie Paule Delplancke Service de Metallurgie et Electrochimie, Universite Libre de Bruxelles, 50 Avenue Franklin Roosevelt, CP 165 1050 Bruxelles, Belgium
Kevin Hubbard Center for Materials Science, MS K765, Los Alamos National Laboratory, Los Alamos, New Mexico 87454 (Received 7 July 1993; accepted 28 April 1994)
Carbon films with up to 32 at. % of nitrogen have been prepared with ion beam assisted magnetron, using a N2 + /N + beam at energies between 50 and 300 eV. The composition and density of the films vary strongly with the deposition parameters. EELS, SXS, XPS, and IR studies show that these a-C: N films are mostly graphitic and have up to 20% sp3 bonding. Nitrogen is mostly combined with carbon in nitrile ( C = N ) and imine ( C = N ) groups. It is shown by RBS and NDP that density goes through a maximum as the average damage energy per incoming ion increases. Positron annihilation spectroscopy shows that the void concentration in the films goes through a minimum with average damage energy. These results are consistent with a densification induced by the collisions at low average damage energy values and induced graphitization at higher damage energy values. These results are similar to what is observed for Ar ion assisted deposition of a-C films. The mechanical properties of these films have been studied with a nanoindenter, and it was found that the hardness and Young's modulus go through a maximum as the average damage energy is increased. The maximum of mechanical properties corresponds to the minimum in the void concentration in the film. Tribological studies of the a-C: N show that the friction coefficient obtained against diamond under dynamic loading decreases strongly as the nitrogen composition increases, this effect being more pronounced at low loads.
I. INTRODUCTION Diamond and diamond-like carbon films are materials of considerable interest because of their special properties: they are hard, with high thermal conductivity, and with high electron and hole mobilities.1 In particular, diamond is the hardest material known, with a hardness value about 100 GPa. In comparison, the second hardest material known is c-BN which lies far behind diamond with a hardness value of 50 GPa. Recently, some reports have been published about the interest of doping carbon films with nitrogen. The main 2440
J. Mater. Res., Vol. 9, No. 9, Sep 1994
motivation for studying C: N films was a paper by Liu and Cohen2 calculating the properties of a hypothetical carbon-nitrogen compound. The model predicts the bulk modulus values of diamond and /3-Si 3 N 4 with good accuracy. When applied to a hypothetical compound /3-C 3 N 4 , where C was replaced by Si in the /3-Si 3 N 4 structure, the results of the calculations indicated that this
Data Loading...
