Raman spectroscopy and mechanical properties of multilayer tetrahedral amorphous carbon films

In order to take the tetrahedral amorphous carbon (ta-C) films as the high acoustic impedence layer in a Bragg reflector isolating acoustic wave from the substrate in solidly mounted resonator, the multilayer films consisting of sp2-rich layers and sp3-rich layers were deposited from a filtered cathodic vacuum arc by adjusting the substrate bias. The microstructure of the films was evaluated using a visible Raman spectroscopy. The stress was calculated according to the changed curvature of the coated and bare substrate. The hardness, modulus and scratching were measured using a nanoindenter. It has been shown that the multilayer structure maintaining high tetrahedral content, high hardness and high elastic modulus is still characterized with lower intrinsic stress and better adhesion.