Influence of the bias-voltage, the argon pressure and the heating power on the structure and the tribological properties of HiPIMS sputtered MoSx films

• Published in: Surface & coatings technology 2020-03, Vol.385, p.125358, Article 125358
• Main Authors: Tillmann, Wolfgang, Wittig, Alexandra, Stangier, Dominic, Moldenhauer, Henning, Thomann, Carl-Arne, Debus, Joerg, Aurich, Daniel, Bruemmer, Andreas
• Format: Article
• Language: English
• Subjects: Argon; Basal plane; Bias; Columnar structure; Crystallography; Densification; Deposition; Deposition parameters; Electric potential; Friction; Heating; HiPIMS; Kinetic energy; Magnetron sputtering; Morphology; MoSx; Random orientation; S/Mo ratio; Sulfur content; Surface energy; Temperature effects; Thin films; Tribofilm; Tribology; Voltage; Wear particles
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2020.125358

Understanding the growth process and its correlation to the structure of MoSx thin films is essential to control the friction behavior. Nevertheless, structural changes related to kinetic and thermal processes occurring during the deposition are not yet fully understood within the context of MoSx sputtered thin films. Therefore, MoSx films were synthesized by HiPIMS (High Power Impulse Magnetron Sputtering) technique using the one factor at a time method. By systematically changing the bias-voltage (0 to −200 V), the argon pressure (200 mPa to 600 mPa) or the heating power (0 to 3000 W) the interaction between the deposition parameters and their impact on the structure and the tribological properties was analyzed.The results show significant differences regarding the influence of kinetic and thermal effects. The investigation of the crystallographic orientation by XRD measurements reveals that a high kinetic energy induced by a high bias-voltage favors the growth of the (100) edge plane. A deposition process with a low deposition temperature and thus a low deposition rate leads to a more pronounced (002) basal plane due to the lower surface energy of the (002) surface. A high kinetic energy is also related to a densification of the morphology and a decrease in the sulfur content, which results in a thicker tribofilm and thus a lower wear and friction. Films deposited with a high heating power on the other show a low friction, but at the same time a columnar microstructure and high wear. Thus, the structure affects the amount of generated wear particles during the sliding, but more important is the ability of keeping them in the contact area during the tribo-tests. •All deposition parameters lead to random orientation of the MoSx thin films.•A high kinetic energy leads to the formation of the (100) edge plane.•The deposition of MoSx thin films with a high bias voltage or high heating power result in a decreased friction.•The generation of third body particles and thus the formation of the tribofilm are affected by the structure of the MoSx thin films.