Solid lubricating films produced by ion bombardment of sputter deposited MoS x films

Abstract

Several attempts to enhance the wear resistance (the “sliding life”) of sputter deposited MoS x films have previously been made. However, sputter deposition of MoS x 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 MoS x 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 × 10 13 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 MoS x layers was related to film structure. Using this approach it was possible to gain valuable information on the relation between MoS x film structure and tribological behaviour. Thus, it was shown that the characteristic columnar plate-like MoS x structure is only obtained when H 2O is present in the plasma, and high fluence (around 1 × 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.