PHASE PERCOLATION TRANSITION AND EMISSION OF EXCITONS IN FILMS WITH CdS QUANTUM DOTS ON A SURFACE OF SiO2

Abstract

Topologically disordered films based on binary mixtures of SiO₂ nanoparticles with CdS quantum dots on their surfaces with different surface and volume concentrations are studied. For the first time, a percolation transition of excitons has been observed in the CdS quantum dots array on a quasi-two-dimensional surface and the features of its formation have been described qualitatively. A percolation transition of excitons in a film based on a binary mixture of pure SiO₂ and coated with quantum dots (SiO₂/CdS), which is analogous to the phase transition of metal and dielectric macroparticles, has also been observed. It is shown that the percolation transition in such a system occurs at a critical concentration of nanoparticles of one sort (n_c ~ 0.6), which is almost twice as high as in the macroparticle system (~0.29). This is due to the interaction between nanoparticles (van der Waals forces and electrostatic forces) and the chemical nature of the binding ligand.