Diamond-like carbon (DLC) is a metastable amorphous material that exhibits\nunique properties. However, there are many limitations regarding the use of\nthis material due to factors such as its tribological characteristics at high\ntemperature and limited thermal stability. In this study, the thermal stability\nand tribological properties of DLC/silicon-nitrogen (DLC/Si-N) composite\nfilms were investigated and compared to those of pure DLC films. All the\nfilms were synthesized using a combination of radio frequency (RF) magnetron\nsputtering and plasma-based ion implantation (PBII) (a so-called sputtering-\nPBII hybrid system) which is newly developed by us. A high purity silicon\nnitride (99.9%) disk was used as the target, applying an RF power in the\nrange of 500 - 700 W and a negative pulsed bias voltage of 5 kV to the substrate.\nAn Ar-CH4 mixture was used as the reactive gas. The CH4 partial\npressure was varied between 0 and 0.15 Pa, while the total gas pressure and\ntotal gas flow were fixed at 0.30 Pa and 30 sccm, respectively. The structures\nof the resulting films were characterized using Raman spectroscopy, while the\nthermal stabilities were assessed using thermogravimetric-differential thermal\nanalysis (TG-DTA) and friction coefficients were obtained via ball-on-disk\nfriction tests. The results indicate that the DLC/Si-N composite films produced\nin this work exhibit improved thermal stability relative to that of pure\nDLC owing to the presence of thermally stable atomic-scale Si-N compound\nin the carbon main flame networks. A DLC/Si-N film containing approximately\n11 at.%Si and 18.5 at.%N shows good thermal stability in air over\n800DegreeC up to 1100DegreeC, together with excellent tribological performance at 500DegreeC\nin air. Overall, the data demonstrate that DLC/Si-N composite films offer\nimproved thermal stability and superior tribological performance at high\ntemperatures.
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