Percolation and excitonic luminescence in SiO2/ZnO two-phase structures with a high density of quantum dots randomly distributed over a spherical surface
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- Bondar, N.V. Semiconductors (2011) 45: 474. doi:10.1134/S106378261104004X
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The results of studies of structures formed of silica (SiO2) nanospheres and ZnO quantum dots randomly distributed over the nanosphere surface to cover an ∼0.45 fraction of the surface area are given. Because of the large surface energy of the spheres, the quantum dots formed on their surface are shaped as disks, wherein charge carriers are influenced by the quantum-confinement effect despite the large disk radii. The disk height is calculated by the effective mass method. The height is found to be comparable with the diameter of excitons in bulk ZnO. Analysis of the optical spectra shows that, at the above-indicated surface area covered with quantum dots, excitons in the array of quantum dots are above the percolation level. The use of some concepts of the percolation theory and knowledge of the topological arrangement of the samples make it possible to obtain quantitative parameters that describe this phenomenon.