Microstructure and surface properties of chromium-doped diamond-like carbon thin films fabricated by high power pulsed magnetron sputtering

• Published in: Applied surface science 2013-07, Vol.276, p.31-36
• Main Authors: Wu, Zhongzhen, Tian, Xiubo, Gui, Gang, Gong, Chunzhi, Yang, Shiqin, Chu, Paul K.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cr-DLC; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; High power pulsed magnetron sputtering; Microstructure; Physics; Surface properties
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2013.02.104

► High C ionization was realized by replacing the pure graphite target to the stably HPPMS discharged Cr target in reactive C2H2 gas. ► Less than 2% Cr atoms were doped in the prepared Cr-DLC films by controlling the poisoning of the target surface induced by reactive gas. ► A smooth surface and a dense structure with high sp3 bond content were obtained due to the intense ion bombardment induced by the highly ionized C flux. ► Compared to the substrate, the Cr-DLC films displayed low friction coefficient and excellent corrosion resistance High power pulsed magnetron sputtering (HPPMS) has attracted much interest due to the large plasma density and high ionization rate of sputtered materials. It is expected to produce a highly ionized C flux from a graphite target but unfortunately, the ionization rate of carbon is still very small and the discharge on a solid carbon target is unstable as well. In this work, a stable discharged chromium target is used in the preparation of chromium-doped diamond-like carbon (Cr-DLC) films in HPPMS in reactive C2H2 gas, but the unstable graphite. The chromium concentration in the Cr-DLC films is limited by surface poisoning due to reactive gas. Less than 2% of Cr is incorporated into the DLC films at C2H2 flow rate of 5sccm or higher. However, as a result of the high ionization rate of the reactive gas in HPPMS, intense ion bombardment of the substrate is realized. The films show a smooth surface and a dense structure with a large sp3 concentration. As the C2H2 flow increase, the sp3 fraction increase and the sp3 to sp2 ratio increase to 0.75at a C2H2 flow rate of 10sccm. Compared to the substrate, the Cr-DLC films have lower friction and exhibit excellent corrosion resistance.