Photoacoustic investigation of the effective diffusivity of two-layer semiconductors

In this work, the problem of the effective thermal diffusivity of two-layer systems is investigated using the photoacoustic spectroscopy. The experime ntal results are examined in terms of the effective thermal parameters of t he composite system determined from a homogeneous material which produces t he same physical response under an external perturbation in the detector de vice. It is shown, that the effective thermal conductivity is not symmetric under exchange of the two layers of the composite; i.e., the effective the rmal parameters depend upon which layer is illuminated in the photoacoustic experiments. Particular emphasis is given to the characterization of the i nterface thermal conductivity between the layer-system.