Long-term thermal stability of Si-containing diamond-like carbon films prepared by plasma source ion implantation

• Long-term stability of silicon-containing diamond-like carbon films investigated
• Annealing for 1 week at temperatures from 523 K to 773 K
• Higher silicon contents suppress thermal degradation.
• Hardness and friction coefficient nearly unchanged for temperatures up to 573 K.
• Higher temperatures led to decreased hardness with friction coefficients still being low.

The long-term stability of silicon-containing diamond-like carbon films was investigated. The samples were prepared by plasma source ion implantation with a mixture of tetramethylsilane (TMS) and acetylene (C2H2) using negative high voltage pulses. The film composition was changed by varying the flow rates of the TMS and C2H2 gases, resulting in a Si content from 0 to 44 at.%. After deposition the films were annealed at temperatures from 523 K to 773 K for 168 h in ambient air. The effect of the Si content on the structure, the mechanical and tribological properties of the DLC films was investigated. A silicon oxide layer is produced on the surface of the film which improves the thermal stability. Mechanical and friction characteristics of the Si-DLC were not much affected by the long-term thermal annealing if the temperature was kept below 573 K.