DEFECTS AND THEIR ROLE IN DETERMINING BULK PROPERTIES OF CRYSTALS.
TEXAS INSTRUMENTS INC DALLAS
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Most impurities in II-VI compounds play a role in luminescence either because they are the luminescence center, or they are photosensitive i.e., they exist in several charge states, or they function as a non-radiative recombination center. Since many of these centers are stable in more than one charge state, prepared by optical excitation at low temperature, the atomic structure of the centers may be deduced from observation of their paramagnetic resonance. Associated optical studies then correlate the paramagnetic center with the luminescence process and excited state structure. This was done for the transition metal, rare earth, and Groups I, III, V, and VII impurity ions. The existence of associates, the occurrence of the Jahn-Teller effect, and resonant energy transfer are among the important phenomena studied. Self-activated luminescence centers have been studied in ZnSe and ZnS Cu3d9 impurity ions have been studied in ZnSe and ZnS, where optical Zeeman effect measurements have observed the CuZn in Td symmetry. The Jahn-Teller effect of Sc3d1 has been studied in detail in CaF2 and SrF2. Rare earth 3 and 2 ions were observed in all of the II-VI compounds associates of the rare earth3 ion with noble metal impurities are observed, and transition metal associates are likewise seen. Finally, luminescence associated with Group V impurities, and population inversion of optically pumped 2S 12 state impurity ions have been discovered. Author
- Solid State Physics