Evaluation of thermal conductivity of porous silicon layers by a photoacoustic method

The paper shows that it is possible to evaluate the thermal conductivity of porous silicon layers by a conventional photoacoustic gas-microphone technique, on the basis of a simple interpretative model for stratified samples. Samples produced by electrochemical etching of crystalline wafers of different type and thickness are considered. The frequency variation of photoacoustic signal, in amplitude and phase, is studied and interpreted by means of a four-layers (air, porous silicon, crystalline silicon, air) model. Thermal conductivity values in the range 2.5-31.2 W/m K are obtained.