Sensitized anti-Stokes luminescence centers in microcrystals of Zn_0.6Cd_0.4S solid solutions with adsorbed dye molecules and few-atomic silver clusters

Abstract

The sensitized anti-Stokes luminescence excited by radiation with wavelengths from 610 to 750 nm and flux densities of 10¹⁴–10¹⁵ quanta/(cm²·s) is detected for microcrystals of Zn _0.6 Cd _0.4 S solid solutions with adsorbed organic malachite green and methylene blue dye molecules. The position of its excitation spectra coincides with that of the absorption spectra of adsorbed dye molecules, which suggests the cooperative mechanism of its occurrence. The possibility of amplification of the anti-Stokes luminescence by means of adsorption of silver atoms and few-atomic silver clusters, in addition to the dye molecules, on the Zn _0.6 Cd _0.4 S surface is investigated. It is assumed that in the latter case, the anti-Stokes luminescence is excited as a result of two-quantum optical transitions with electron or electron excitation energy transfer from the dye molecules adsorbed on the Zn _0.6 Cd _0.4 S surface to silver atoms and few-atomic silver clusters creating deep local states with photoionization energies of 1.8–2.0 eV in the gap.