PUB - Publikationen an der Universität Bielefeld

MoSx films with interlayers of Cr3Si or Cr were deposited onto steel substrates by means of rf magnetron sputtering, The coating parameters such as the working pressure p(Ar), the rf power P, the target-substrate distance (TSA), as well as the deposition mode (intermittent or stationary) were varied. The chemical composition of the MoSx films is essentially determined by the coating parameter TSA. Reduction of the TSA, as well as increasing p(Ar) and lowering P, results in a decrease in the sulphur and increases in the oxygen, carbon and hydrogen contents. Mechanical stress in the MPa range is observed in the MoSx films, which decreases with increasing p(Ar). The microstructure of the MoS2 films is found to be nanostructured, and is very strongly influenced by the sputtering process conditions. The films are neither amorphous nor nanocrystalline in the sense of a three-dimensional lattice. The atomic structure differs from that of crystalline bulk molybdenum sulphide by a high degree of stacking faults. There is no crystallographic correlation between atoms of neighbouring MoS2 layers at distances of more than 0.67 nm. The number and regularity of the stacking of the a-b basal lattice planes in the c-direction, as well as the range of ordering of the atoms within the a-b planes, are influenced by the preparation conditions. The grain sizes and the range of crystal-like order are limited to a few nanometers. The tribological properties are characterized by the number of revolutions up to 80 000 at a load of 10 N; the highest values are achieved when using larger TSA and p(Ar) greater than or equal to 1.3 Pa. The wear resistance of the films is correlated with the range of crystal-like order in the a- and b-directions, as well as with the range of correlated stacking of the layers in the c-direction. (C) 1997 Elsevier Science S.A.