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Semiconductors

, Volume 50, Issue 3, pp 364–371 | Cite as

Photoluminescence and Confinement of Excitons in Disordered Porous Films

  • N. V. BondarEmail author
  • M. S. Brodin
  • A. M. Brodin
  • N. A. Matveevskaya
Microcrystalline, Nanocrystalline, Porous, and Composite Semiconductors

Abstract

The exciton confinement effect in quantum dots at the surface of SiO2 spheres and the percolation phase transition in films based on a mixture of pure SiO2 spheres and spheres covered by CdS quantum dots (SiO2/CdS nanoparticles) are studied. It is found that, due to the high surface energy of spheres, the quantum dots deposited onto their surface are distorted, which modifies the exciton confinement effect: the effect is retained only in one direction, the direction normal to the surface of the spheres. As a result, the energy of the exciton ground state exhibits a complex dependence on both the quantum-dot radius and sphere size. In the optical spectra of films based on this mixture, the clustering of small-sized nanoparticles and then, at a critical concentration of nanoparticles of ~60%, the formation of a percolation cluster are detected for the first time. The critical concentration is twice higher than the corresponding quantity given by the model of geometrical “colored percolation”, which is a consequence of interaction between submicrometer nanoparticles. The relation between the basic parameters of the percolation transition, such as the film porosity, coordination number, and the quantity defining the number of particles in the percolation cluster, is obtained and analyzed.

Keywords

Percolation Threshold Diffusive Reflectance Spectrum Percolation Cluster Percolation Transition Exciton Ground State 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Pleiades Publishing, Ltd. 2016

Authors and Affiliations

  • N. V. Bondar
    • 1
    Email author
  • M. S. Brodin
    • 1
  • A. M. Brodin
    • 2
  • N. A. Matveevskaya
    • 3
  1. 1.Institute of PhysicsNational Academy of Sciences of UkraineKyivUkraine
  2. 2.National Technical University of Ukraine “KPI”KyivUkraine
  3. 3.Institute for Single CrystalsNational Academy of Sciences of UkraineKharkivUkraine

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