712 共振/レーザー法による薄膜の弾性定数測定と内部組織のマイクロメカニックス評価(GS-3 超音波計測)

Abstract

We originally develop a measurement method for determining anisotropic elastic constants of thin films on substrates. It uses free-vibration resonance frequencies of a film/substrate rectangular parallelepiped specimen, which depend on dimensions, mass density and elastic constants of the film and substrate; film's elastic constants are inversely determined from the resonance frequencies. We measure the resonance frequencies with a high accuracy using a piezoelectric tripod transducer, consisting of needle-type transducers for generation and detection of vibration. Detected resonance peaks are identified by measuring the displacement distribution on the vibrating surface using laser-Doppler interferometer. We applied this method to copper and CVD diamond thin films. Their elastic constants show elastic anisotropy between the in-plane and out-of-plane directions. We attribute it to incohesive bonds at grain boundaries. This view is supported by micromechanics calculations.