Deposition and properties of superhard and hydrogen-free a-C/ta-C multilayer systems prepared by PLD

The exceptional mechanical and chemical properties of superhard ta-C coatings make them highly versatile for various applications. However, challenges such as the high stiffness ratio between the film and substrate, insufficient toughness, limited adhesion, and internal stresses restrict their broader application. In this study, superhard, hydrogen-free a-C/ta-C multilayer systems were produced using pulsed excimer laser deposition (PLD) with the objective of optimizing their mechanical properties compared to ta-C single layers. Pulsed laser annealing was applied to reduce internal stresses, particularly in tetrahedral amorphous carbon (ta-C) layers. The sp 2 /sp 3 hybridization of the carbon layers was characterized by Raman spectroscopy, and their mechanical properties were assessed using nanoindentation and pin-on-disk tribological measurements. The results indicate that variations in the number of layers and the thickness of individual sublayers lead to a significant improvement in adhesion, while the mechanical properties of the multilayers were comparable to those of single ta-C layers.