Impact of thermal annealing on photoacoustic response and heat transport in porous silicon based nanostructured materials

Features of heat transport in silicon-based porous structures with different morphology before and after thermal annealing are investigated. Specifically, fractal-like porous silicon and silicon nanowire arrays samples were considered. All the structures were annealed in dry air at various temperatures in diapason from 600 °C up to 1000 °C for 20 minutes. The photoacoustic technique with gas-microphone registration was applied for the thermal diffusivity evaluation of the samples. Particularly, the amplitude frequency dependencies of photoacoustic response from the considered samples in the classical gas-microphone configuration were measured in the range from 10 Hz to 3 kHz. The simulation of the experimental dependencies with the use of appropriate model allowed us to evaluate thermal conductivity. It was found that the short time thermal annealing together with increasing annealing temperature leads to significant reduction of thermal transport in mesoporous silicon. On the opposite, the thermal properties of silicon nanowires remain unaffected.