Visible light emission from porous silicon examined by photoluminescence and Raman spectroscopy

摘要

We describe the simultaneous acquisition of Raman and photoluminescence (PL) spectra on porous silicon (PS) samples that emit visible light. Spectra were acquired in both ex situ experiments (after exposure to air) as well as in situ experiments (with the PS covered either with the hydrofluoric acid electrolyte used in the formation process or water). In one set of ex situ experiments, we observed an inconsistency in the shift of the wavelength of maximum luminescence intensity for PS samples that exhibit oxygenated character in the Raman spectra. A higher current density produced a red shift in the PL spectra in one experiment, while chemical dissolution of the PS by hydrofluoric acid produced the well-known blue shift in another case. In two in situ experiments, we observed very weak and red-shifted PL for a PS sample immersed in HF (compared to the same sample measured later in air) while in another we immersed air-exposed PS in water and observed a 15-fold increase in PL intensity along with a blue shift in the luminescence maximum.