Elastic anisotropy and incohesive bond of chemical-vapor-deposition diamond film: Acoustic resonance measurements and micromechanics modeling.

This article studies elastic anisotropy of chemical vapor deposition (CVD) polycrystalline diamond films using acoustic spectroscopy and micromechanics modeling. CVD diamond films often exhibit elastic anisotropy between the film-growth direction and in-plane direction and show five independent elastic constants. They are denoted by C[sub 11], C[sub 33], C[sub 13], C[sub 44], and C[sub 66] when the x[sub 3] axis lies along the film-growth direction. Measurements of thickness resonance frequencies and free-vibration resonance frequencies of the diamond film deduce four independent elastic constants among them, including C[sub 44] and C[sub 66], with which the elastic anisotropy is discussed. The anisotropy between the shear moduli is 5%–10%. The elastic constants are remarkably smaller than those of 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. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]