Measurement of the Anisotropic Elastic Constants of CVD Diamond Film and Micromechanics Modeling

This paper studies the anisotropic elastic constants of a CVD polycrystalline diamond film using acoustic spectroscopy and micromechanics modeling. Many films exhibit elastic anisotropy between the film-growth direction and inplane direction and possess five independent elastic constants; they are C11, C33, C12, C13 and C44 when the x3 axis is along the film-growth direction. Combination of resonance ultrasound spectroscopy (RUS) and electromagnetic acoustic resonance (EMAR) deduces the four independent elastic constants among them, including C44 and C66, with which the elastic anisotropy is discussed. We found 5-10% anisotropy between them and considerably small elastic constants compared with an isotropic polycrystalline diamond. We attribute the anisotropy and small elastic constants of the CVD diamond film to local incomplete cohesion. This view is supported by a micromechanics calculation.