Photoacoustic measurement of thermal properties and thickness of buried layers in a multilayer film

摘要

The photoacoustic model of multilayer with a strong-absorbing surface layer is developed. The phase of ph0toacoustie signal is measured as a function of modulated frequency using apparatus totally controlled by a computer system. The thermal diffusivity, effusivity as well as thickness of several buried layers are obtained independently through the best fit of experimental data according to the theoretical model. The multilayers of thin metal and alloy film are investigated. This method is proved to be valuable particularly in nondestructive examination of subsurface physical properties.