Photoluminescence and Raman spectroscopy of silicon thin films grown by laser ablation

Silicon thin films were prepared by Laser Ablation technique onto fused quartz substrates. The effect of thermal annealing on the silicon films and the pressure and temperature dependence show an unusual behavior of photoluminescence (PL) spectra of the silicon (Si) thin films. An intense PL energy band around 3.0 eV (400 nm) was observed at room temperature after thermal annealing. Raman spectra of the samples showed an asymmetric peak shifted to 517 cm⁻¹, in comparison with the crystalline Si optical phonon at 520 cm⁻¹; a broadening (7 cm⁻¹) of the phonon line is also observed. These results agree quiet well with the relaxation of the q-vector selection rules for the Raman active optical phonons. The red-shifted asymmetric Raman line shape was fitted by using the phonon-confinement model, in order to estimate the size of the particles constituting the films.