Landau-Placzek ratio of an inorganic glass with PbS quantum dots

The first example of application of the Rayleigh and Mandel'shtam-Brillouin scattering (RMBS) spectroscopy to a study of glass containing quantum dots (QDs) is presented. PbS QDs were precipitated in sodiumsbnd zincsbnd aluminosbnd silicate glass doped with lead sulfide during successive heat treatment in several steps. After each step of the heat treatment, RMBS and absorbance spectra were measured. As a result, the Landau-Placzek ratio and QDs radii were evaluated as functions of heat treatment time. It was found that the Landau-Placzek ratio rises in the course of heat treatment by an order of magnitude. We connect this rise with an increase in Rayleigh scattering caused by increase of radii and number density of QDs. To confirm this assumption, the theoretical expression for the contribution of light scattering by QDs to the Landau-Placzek ratio was derived. The theoretical dependence of the QDs Landau-Placzek ratio on radius and number density of QDs is confirmed by the experiment. For calculation of this Landau-Placzek ratio, optical constants for PbS taken from different literature sources were used. Only the use of data from [S. Adachi (1999) Optical Constants of Crystalline and Amorphous Semiconductors] gives a good agreement between the calculated and measured values.