Porosity-induced blueshift of photoluminescence in CdSe

Porous CdSe layers have been fabricated by anodic etching of $n$-type single crystalline substrates with different values of conductivity. The morphology and porosity of the layers thus produced were found to be controlled by the conductivity of the material, anodization voltage, and conditions of in situ UV illumination. The porosity-induced changes in the photoluminescence spectra were studied. The decrease of the skeleton size down to $10–20nm$ was found to result in a blueshift of the excitonic emission lines by $10meV$ which was attributed to quantum-size effects in the nanocrystalline CdSe porous skeleton. An increase of the exciton–LO-phonon interaction by a factor of 1.5 in a weak-to-intermediate confinement regime was deduced from the analysis of temperature dependence of the free exciton luminescence line.