Local complex emission centers in the wide band gap materials: theoretical predictions and experimental diagnostic possibilities

Sergiy G. Nedilko 

Department of Physics, Taras Shevchenko Kyiv University, 6 Gloushkov avenue, Kyiv 252022, Ukraine

Abstract

The paper concerns mainly to the statement of the study of a role of complex defects to determine emission (luminescence) properties of the oxide wide and gap optical materials.
Luminescence centers (LC) of materials constructed by cation and anion sublattice with the last formed by molecular groups are considered as containing both the "core" of the center and the neighborhood elements of the crystal matrix. The "core" can be simple, one centered, or two centered. The first is either admixture atom, molecule (charged or not) or own defect of matrix. The second is complex center that combines the simple "core" that determines principal characteristics of electron-vibronic transitions of the LC and some either own defects of matrix or admixtures. The interaction between two components of complex center determines the spectral - kinetic characteristics of the complex centers on the whole.
The electronic system of the complex LC is united, that especially concerns of the exited electronic states, besides it should to be considered as non-adiabatic system which is described in the frames of Jahn Teller effect (conjugated electron-vibronic states). It is particularly important when the "core" of LC is a molecule. These centers were formerly called by us as "ion-polaron" pairs.
These properties result in a sensitivity of the LC to changing of structure, composition, presence of impurities and defects, temperature and other external factors.
The paper draws attention to experimental observation of mentioned properties for some complex oxide materials (chromates, phosphates, tungstates, ) via:
- Zero-phonon lines (ZPL) behaviors;
- Temperature dependencies of luminescence kinetics;
- Local phase transitions;
- Formation of microcrystalline inclusions on the basis of "own" chemical components

 

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Presentation: poster at E-MRS Fall Meeting 2003, Symposium A, by Sergiy G. Nedilko
See On-line Journal of E-MRS Fall Meeting 2003

Submitted: 2003-05-10 16:21
Revised:   2009-08-25 11:34