Measurements of Thin-Film Elastic Properties by Line-Focus Acoustic Microscopy
Quantitative acoustic microscopy has been used to measure the velocity of leaky surface acoustic waves (SAWs) [1,2]. This technique measures a V(z) curve, which is a record of the voltage output V of the transducer as a function of the distance z between the acoustic lens and the specimen. Line-focus acoustic microscopy (LFAM) allows the measurement of the SAW velocity in specified directions. In earlier papers, LFAM has been used to determine the elastic constants of isotropic thin films [3,4] and anisotropic thin films [5–7]. The directional variation of the SAW velocity of a thin-layer/anisotropic substrate configuration may be quite different from that of the bare substrate. It follows that this variation can be used to determine the elastic properties of thin films.