Elastic Properties of CVD Diamond via Dynamic Resonance Measurements
Mark P. D'Evelyn, David E. Slutz, Bradley E. Williams, General Electric Corporate R & D, General Electric Superabrasives
Control of the mechanical properties of CVD diamond is essential to achiev optimal performance in various applications. While several methods have been applied to the measurement of Young’s modulus of thick-film CVD diamond, in general these methods are not suitable for diamond characterization on a production scale. In addition, many of these methods cannot determine the shear modulus (or Poisson’s ratio), which is necessary for a complete description of the elastic properties. We have developed a simple dynamic resonance method for determining both the Young’s modulus and shear modulus of free standing CVD diamond in the shape of rectangular plates or round discs. The specimen is supported along nodal lines of flexural or torsional modes. Oscillations are induced by impact from a falling ceramic bead, are senses by a microphone, and the resonant frequencies are determined by a signal analyzer. The Young’s and shear modulus are calculated from the frequencies of the fundamental flexural and torsional modes, respectively, using quasi-analytic formulas. CVD diamond grown by several methods routinely achieves Young’s and shear modulus values above 1000 Gpa and 500 Gpa, respectively, in good accord with theoretical values for pure polycrystalline diamond.