Correlation between the H+ concentration in the electrolyte and the photoluminescence of porous silicon

We have investigated the photoluminescence (PL) properties of porous silico n (PS) samples prepared in a 20% HF-ethanol electrolyte with different H-da gger concentration by varying the added HCl or NH3 . H2O concentration in t he range of 0-6 mol/l at a constant anodic current density. The PL spectra continuously blueshift with increasing NH3 . H2O concentration or decreasin g HCl concentration in electrolyte. Meanwhile, the infrared absorption asso ciated with Si-O gradually increases with the NH3 . H2O concentration. Rama n scattering results indicate that the average particle sizes of the PS sam ples have no obvious evolution with varying H+ concentration in electrolyte . These experimental results strongly support that light emission of PS ori ginates from luminescent centers.