Raman investigation of orthorhombic M^IIGa₂(S, Se)₄compounds

Abstract

Raman investigation of isostructural polycrystalline MII Ga 2 (S, Se)4 compounds with MII = Pb, Sr, Eu, Yb and Ca was performed. We observed that the effect of MII atomic mass on the phonon frequencies is negligible and that the vibrations are essentially influenced by the sizes of the MII cations. As the effects of cation substitution are small we concluded that the orthorhombic thiogallates MII Ga 2 S4 exhibit nearly the same phonon energies: about 280 cm−1 (∼35 meV) and 360 cm−1 (∼45 meV) for the most intense vibration modes. The substitution of S atoms by heavier Se atoms causes the shift of the Raman spectrum to lower frequencies. The orthorhombic MII Ga 2 Se4 compounds present phonon energy at about 185 cm−1 (∼23 meV) for the most intense vibration mode. Results confirm that a molecular model is more adequate to describe the vibrations of these compounds than the factor-group analysis.

Photoluminescence of Eu2+ in SrGa2S4

“…It is coherent with the results obtained by Raman spectroscopy [23]. In this previous study, the most intense Raman mode of the SrGa 2 S 4 spectrum was found at 34.5 meV.…”

Cathodoluminescence and Longevity Properties of Potential Sr1-xMxGa2S4:Eu (M = Ba or Ca) Green Phosphors for Field Emission Displays

“…[3][4][5][6][7] These reports indicated that Eu or Ce doped thiogallate phosphors exhibit excellent intrinsic efficiency, color purity, and current saturation behavior. Recent studies have also shown that the luminescence efficiencies of SrGa 2 S 4 :Eu and CaGa 2 S 4 :Eu are little affected by thermal quenching, [8][9][10] and have confirmed that SrGa 2 S 4 :Eu and CaGa 2 S 4 :Eu are suitable phosphors for lighting and display devices, especially for applications where heat effects are expected. However, the operational voltage requirements of FEDs have changed from low voltages (< 2 kV) to moderate voltages (2-10 kV), because carbon nanotube (CNT)-FEDs use higher voltage e-beams than Spindt-type FEDs in order to obtain greater brightness and longer lifetimes.…”

Термостимулированная люминесценция кристалла Ca(Al-=SUB=-x-=/SUB=-Ga-=SUB=-1-x-=/SUB=-)-=SUB=-2-=/SUB=-S-=SUB=-4-=/SUB=-:Eu-=SUP=-2+-=/SUP=-

“…44296.16340 Легированный редкоземельными элементами (РЗЭ) тиогаллат каль-ция (CaGa 2 S 4 ) является перспективным материалом в оптоэлектронике и фотонике [1]. Максимальная энергия фононов и хорошие оптические свойства позволяют получать высокоэффективные люминофоры, а элек-тропроводность бывает пригодна для создания электролюминесцентных дисплеев [2][3][4] [5][6][7][8][9][10]. CaGa 2 S 4 с примесью эрбия дает фотолюминесцен-цию на длине волны 1554 nm, что подходит для применения его в телекоммуникации [11].…”