Temperature dependence of mechanical properties of DLC/Si protective coatings prepared by PECVD

One of the main problems of amorphous diamond-like carbon (a-C:H or DLC) films deposited by plasma-enhanced chemical vapor deposition (PECVD) is their poor thermomechanical stability. The thickness of the films is limited to a few hundreds of nanometers in order to guarantee stable coatings. It is shown that major improvements in the mechanical properties of DLC films can be obtained if hexamethyldisiloxane is added in the gas mixture used for DLC deposition. The mechanical properties of hard protective DLC/Si films deposited by PECVD from an argon-methane-hexamethyldisiloxane mixture have been analyzed using microindentation techniques as the main experimental characterization tool. The formation and development of crack lines and patterns have been studied in order to determine the fracture toughness of the film and of the interface as a function of temperature.