Contributions of the interior and surface states of charge carriers to the emission spectra of CdS quantum dots in borosilicate glasses

The photoluminescence spectra of CdS quantum dots grown in a borosilicate glass by sol-gel technology are recorded and analyzed. It is shown that the photoluminescence spectra of the samples are related to annihilation of free (interior) excitons in the ground state and excited state. Emission associated with the surface states of the quantum dots is detected in the region around 2.7 eV for the first time. The emission is due to recombination of electrons localized at the surface with heavy holes in the free states of the quantum dots. Resonance excitation of the structures makes it possible to reveal the specific features of the localized surface states responsible for the photoluminescence band. The properties of the band are, to a large extent, similar to the properties of the emission bands of both three-dimensional media (amorphous semiconductors and substitution alloys) and two-dimensional systems (quantum wells and superlattices).