Laser-Induced Melting of Porous Silicon

Abstract

The dynamics of laser-induced melting of porous silicon (por-Si) irradiated in vacuum by nanosecond pulses of a XeCl laser (wavelength 308 nm) is investigated by time-resolved reflectivity method. The laser-induced modifications of por-Si are monitored by SEM, FTIR and photoluminescence spectroscopy. The threshold of laser-induced melting of por-Si is found to decrease from 35 to 11 mJ/cm2 with the increase of porosity from 45% to 82%, while the melting threshold of c-Si is 750 mJ/cm2. A comparison between the experimental data and results of simulations shows that the decrease of thermal conductivity and the lowering of por-Si melting temperature are the main reasons for the diminution of the melting threshold with the increase of porosity.