PHOTOLUMINESCENCE IN ALPHA-ZNAL2S4 AND ALPHA-ZNAL2S4-ER3-CRYSTALS( SINGLE)

alpha-ZnAl2Se and alpha-ZnAl2S4:Er3+ single crystals were grown by the chemical transport reaction method. They crystallized in the spinel s tructure. The indirect energy band gaps of the alpha-ZnAl2S4 and alpha -ZnAl2S4:Er3+ Single crystals at 10 K were found to be 3.860 eV and 3. 724 eV, respectively, and also the direct energy band gaps were found to be 4.140 eV and 4.037 eV, respectively. In the photoluminescence (P L) spectrum of the alpha-ZnAl2S4 single crystal at 13 K, broad peaks a ppeared at 481, 957, and 1289 nm. In the PL spectrum of the alpha-ZnAl 2S4:Er3+ single crystal at 13 K, broad peaks were observed at 504, 984 , and 1304 nm, and in addition to them, sharp PL peaks appeared in the wavelength ranges 413 similar to 418 nm, 552 similar to 563 nm, 764 s imilar to 796 nm, and 1506 similar to 1576 nm. These sharp PL peaks in the alpha-ZnAl2S4:Er3+ single crystal were attributed to the electron transitions from the split levels of the H-2(9/2), S-4(3/2), I-4(9/2) , and I-4(13/2) excited states of the Er3+ ion in the T-d symmetry sit e to the split levels of the I-4(15/2) ground state.