Luminescence of Ca0.5Ba0.5Ga2S4 crystals activated by Eu2+ and Er3+ ions

Abstract

The photoluminescence (PL) in the visible spectral range of Ca 0.5 Ba 0.5 Ga 2 S 4 solid solutions activated with ions of rare-earth elements Eu 2+ and Er 3+ has been studied in the temperature range of 10-300 K. The PL spectrum contains a strong luminescence band peaking at 530 nm, which is due to the 4 f 6 5d → 4 f 7 transitions in Еu 2+ ions and weak lines in the range of 650-675 nm, which are due to the 4 F 9/2 → 4 I 15/2 transitions in Er 3+ ions. The position of the PL spectrum and the total PL intensity are characterized by high temperature stability in the range of 10-300 K; the total PL intensity decreases by only 13% with respect to the maximum value at 10 K. The PL decay time and the activation energy of nonradiative recombination channels are found to be τ e = 291 ns and E a = 41 meV, respectively. INTRODUCTIONPhotoluminescence (PL) of ions of rare-earth elements (REEs) in wide-gap semiconductors has been intensely investigated, because these compounds are characterized by high luminescence efficiency due to the excitation of REE-ion PL through the semiconductor matrix [1][2][3]. A study of the luminescence properties of REEs in semiconductors and insulators yields information about the nearest REE environment and the symmetry of PL centers and crystal field. Ternary alkali-earth chalcogenide semiconductors of the II-III 2 -VI 4 type (II: Ba, Sr, or Ca; III: Ga or Al; and VI: S, Se, or O), activated by REE (Eu, Ce, Er, Yb, Pr, or Sm) ions, are promising phosphors.Calcium thiogallates doped with Еr 3+ ions exhibit strong Stokes and anti-Stokes luminescence in the visible spectral range at wavelengths of 530 nm ( 2 H 11/2 → 4 I 15/2 ), 550 nm ( 4 S 3/2 → 4 I 15/2 ), and 660 nm ( 4 F 9/2 → 4 I 15/2 ) and in the near-IR region at 870-920 nm ( 4 S 3/2 → 4 I 13/2 ), 976 nm ( 4 I 11/2 → 4 I 15/2 ), and 1530 nm ( 4 I 13/2 → 4 I 15/2 ) [4,5]. Barium, strontium, and calcium thiogallates activated by Eu 2+ ions are efficient phosphors emitting in the blue-green spectral region due to the 4 f 6 5d → 4 f 7 electronic transitions [6][7][8][9][10].Luminescence efficiency can be increased using more than one type of REE ions as dopants due to the excitation-energy transfer from one REE ion to another. In particular, in barium thiogallates activated

Optical and Dynamic Properties of ZnGa2S4

“…High photoluminescence (PL) intensity and efficiency, high optical activity, wide bandgap are the main characteristics of these types of materials. [1][2][3][4][5][6][7] All mentioned features indicate high perspectives of these compounds in different directions of science and technology. ZnGa 2 S 4 was synthesized first in the study by Hahn et al [4] It was determined that the crystal structure of ZnGa 2 S 4 is tetragonal symmetry with lattice parameters a ¼ 5.496 Å, c ¼ 10.99 Å, c/a ¼ 2.…”