The study of mechanical properties of a-C:H films by Brillouin scattering and ultralow load indentation

Abstract

In this study diamondlike a-C:H films have been prepared by different methods: In our first experiment a-C:H films were deposited by plasma decomposition of methane at different bias voltages. In the second experiment a-C:H films with high hardness were implanted with 400-keV C+ ions and different doses between 1013 and 1017 ions/cm2 . Subsequently, the following mechanical properties of the films were measured: The shear modulus μ by the frequency of the surface phonon (Rayleigh wave), the stiffness S by an ultralow load indentation of diamond. The Young’s modulus and the Poisson’s ratio were calculated from μ and S. The internal stress σ was determined with the bending beam method. From the Young’s modulus E and the internal stress σ, the average strain ε of the films has been calculated. From the behavior of ε it was concluded that a phase transition from amorphous diamondlike to amorphous graphitelike a-C:H films occurred with increasing substrate bias voltage.