SOLID LUBRICATING FILMS PRODUCED BY ION-BOMBARDMENT OF SPUTTER DEPOSITED MOSX FILMS

Several attempts to enhance the wear resistance (the "sliding life") of sputter deposited MoSx films have previously been made. However, sputter deposition of MoSx films is often difficult to control owing to changes in substrate temperature and presence of water vapour in the plasma during deposition. In the present study MoSx films were deposited under extremely well controlled conditions with respect to both the deposition temperature and the water vapour pressure. 400 keV Ar+ bombardment, performed after film deposition at doses varying from 3 x 10(13) Ar+ cm-2 to 1 x 10(16) Ar+ cm-2 is shown to have a minor influence on film composition, and a marked influence on film structure. The ion bombarded films were subjected to tribological investigations and the sliding life of the various ion bombarded MoSx layers was related to film structure. Using this approach it was possible to gain valuable information on the relation between MoSx film structure and tribological behaviour. Thus, it was shown that the characteristic columnar plate-like MoSx structure is only obtained when H2O is present in the plasma, and high fluence (around 1 x 10(16) Ar+ cm-2) ion beam enhanced sliding life is only found when bombarding these plate-like films. Furthermore, it is shown that the presence of substantial amounts of oxygen in the films (about 25 at.%) is not detrimental to the tribological behaviour, unless the oxygen induces inferior plate-like structures.