Carrier density and confined polaron effects in the photoluminescence of fresh and oxidized porous silicon

Abstract

In this report the temperature-dependent photoluminescence spectra, Fourier transform infrared (FTIR) spectra and time-resolved FTIR spectra of freshly prepared porous silicon and oxidized porous silicon are examined. The experimental results indicate that there is a gradual transformation of electronic states with ageing in air, because ageing led to the surface oxidation and size reduction of Si nanostructures. This surface variation from hydrogen to oxygen during ageing leads to a red shift of the emissions. A clear quantum-confinement effect exists for both H-and O-capped porous silicon but the emissions in O-capped porous silicon show clear polaronic nature. The photoinduced polaron is evidenced by the time-resolved FTIR results. A reversible H-detrapping process in silicon wafer occurs with temperature, which influences the conduction of silicon wafer and the photoluminescence of as-prepared porous silicon due to the carrier density changes.

Broadband dielectric spectroscopy of oxidized porous silicon

“…One can clearly observe a blue shift in the PL peak wavelength with oxidation time, which has been attributed to the shrinking in size of the Si nanocrystals until saturation [12]. Note that a similar, but not identical, behaviour has been found for aged PS samples which were oxidized in air [19] and for anodicallyoxidized PS [21] when exposed to various atmospheres [20].…”