Phase Per Colation Transition and Emission of Excitons in Films With CdS Quantum Dots on SiO2 Surface

Abstract

Topologically disordered films based on binary mixtures of SiO2 nanoparticles with CdS quantum dots on their surface 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 fi lm based on a binary mixture of pure SiO2 spheres and those 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 (nc ~ 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.