On the hydrogenated silicon carbide (SiCx:H) interlayer properties prompting adhesion of hydrogenated amorphous carbon (a-C:H) deposited on steel

• SiCx:H interlayer thickness decreases at higher deposition temperatures.
• Temperatures higher than 300 °C guarantee the a-C:H film adhesion on steel.
• Adhesion is associated with the nature of chemical bonds formed in the interlayer.

This work reports a systematic study of physical–chemical properties of SiCx:H interlayers deposited by using tetramethlysilane on AISI 4140 at different temperatures (100 °C–550 °C) and its effects on the adhesion of a-C:H thin films. The bi-layers were obtained by pulsed-DC PECVD assisted by electrostatic confinement. The results show that the thickness of the SiCx:H interlayer exponentially decreases as the deposition temperature increases, i.e., a thermally activated kinetic process controls the global chemical reaction in the interlayer. There is a transition temperature (∼300 °C) for interlayer deposition where adhesion of a-C:H is reached. Above ∼300 °C, the a-C:H thin films show critical loads to wedge spallation from 298 (300 °C) to 478 mN (550 °C). At higher temperatures, H and Si contents decrease whereas C content increases in the interlayer. The improved adhesion is associated with the nature of chemical bonds formed in the interlayer.