INFLUENCE OF LOCAL ELECTRIC FIELDS ON THE PHOTOLUMINESCENCE OF CdS NANOCRYSTALS ON THE OXIDIZED MACROPOROUS SILICON SURFACE

Oxidized macroporous silicon structures with CdS surface nanocrystals have been proposed to enhance the photoluminescence of CdS nanoparticles due to reducing the electron recombination outside the nanoparticle layer. It has been found that the resonance electron scattering on the Si–SiO2 interface for samples with low concentration of Si–O–Si states transforms into scattering on ionized surface states for samples with high concentration of Si–O–Si in the structured oxide. The maximum intensity of photoluminescence was measured for a structure with the maximal strength of the local electric field at the interface of silicon matrix with the structured oxide. It indicates a significant decrease of non-radiative recombination of electrons generated in CdS nanocrystal layer due to the counter flow of electrons from the silicon matrix towards the nanocrystals layer. The quantum yield of photoluminescence increases with time due to evaporation of water molecules.