COMPOSITION AND STRUCTURE OF REACTIVELY SPUTTER-DEPOSITED MOLYBDENUM-CARBON FILMS

MoCx films were grown by d.c. reactive sputtering in an Ar-CH4 atmosph ere onto MgO (001) single-crystal surfaces. The crystallographic struc ture of the films was revealed by reflection and transmission high-ene rgy electron diffraction. The microstructure was studied by transmissi on electron microscopy and the composition of the films was determined by Auger electron spectroscopy. Under the used processing conditions, the electron diffraction shows that only MoC with the B-1 structure ( NaCl-type) was formed. The carbon content of the films was found to in crease with increasing CH4 partial pressure and the lattice parameter of the B-1 phase was also found to vary in the same direction as a con sequence of an increase of incorporated carbon in the B-1 lattice. The determined values for lattice parameters and carbon contents, in the carbon-richer side, were somewhat greater than the highest ones report ed for the rapidly quenched B-1 phase. This fact was related to an ext ension of the homogeneity range of this phase. The results may be attr ibuted to lower deposition rates which seem to play a prominent role. In agreement with previous studies performed on analogous reactively s puttered M-C systems, the grain size was found to decrease when the co ncentration of reactive gas is increased. This behavior may be interpr eted in terms of carbon location at the grain boundaries as well as in terms of a reduction of the mean migration paths of adatoms caused by an increase of the substrate impinging Bur resulting from more CHn ra dical formation.