Photothermal examination of buried layers

Abstract

The influence of a buried layer within a sample on the propagation of thermal waves is determined by measuring the phase and amplitude of the photothermal signal during periodic illumination. The results are in agreement with the calculation that follows a thermal-wave approach involving a three-layer sample and a Lambert–Beer-like distribution of the heat source in the covering layer. In this way determination of the thickness or thermal properties of buried layers even much thinner than their thermal-diffusion length is possible.