Photo-acoustic characterization of porous silicon samples

The photoacoustic technique is used largely for the thermal and optical non-destructive characterization of materials. In this paper we present a new and alternative method for the measure of thermal conductivity in porous silicon by considering the photoacoustic response at fixed frequency of samples with the same porosity but different thickness. The analysed samples are fabricated by etching n-type, 1 Omega cm, 550 mu m thick crystalline silicon; they have a porosity ranging from 40-70% and thickness from 45-250 mu m. The measured thermal conductivity is lower than the one reported for crystalline silicon by two orders of magnitude.