Dispersion of Principal Refractive Indices of CaGa<sub>2</sub>S<sub>4</sub>

Shim, YongGu; Kondo, Shinya; Kataoka, K.; Wakita, Kazuki; Abdullayeva, S.G.; Mamedov, Nazim

doi:10.1143/jjap.47.8178

Cited by 1 publication

(1 citation statement)

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“…In the present study, the absolute reflectivity were calculated using the experimental data on the dispersion of refractive index n(E) in the transparent region [8] and the relation R(E) = {n(E) -1} 2 / {n(E) + 1} 2 . The reflectivity spectrum measured above the fundamental absorption edge at 300 K was connected to the calculated one by multiplying with a constant factor.…”

Section: Resultsmentioning

confidence: 99%

Excitation processes of trivalent cerium ions in calcium thiogallate crystals by hot photocarriers

Kitaura

Ohnishi

Sasaki

et al. 2010

IOP Conf. Ser.: Mater. Sci. Eng.

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Abstract. Excitation spectra for the 5d → 4f emission of Ce 3+ ions in CaGa 2 S 4 crystals have been measured at 300 K by using vacuum ultraviolet (VUV) photons, together with reflectivity and absorption-edge spectra. X-ray photoelectron spectroscopy (XPS) experiment has also been performed in order to clarify the contribution of shallow core states to the excitation and reflectivity spectra. Furthermore, cluster calculation by a relativistic discrete variational X (DV-X method has been carried out to elucidate the optical transitions resulting in the creation of multiple e-h pairs in CaGa 2 S 4 . The excitation processes of Ce 3+ ions in CaGa 2 S 4 by hot photocarriers are discussed on the basis of the electronic structure determined from the experiments and calculation. IntroductionLuminescence properties of inorganic phosphors have been studied toward applications for flat panel display and solid-state lighting. Development of inorganic phosphor devices is achieved through continuous investigation of phosphor materials. Since fundamental researches were focused on ternary compounds such as II-III-VI group for the past 10 years [1], some bright phosphors were synthesized using alkaline-earth thiogallates and thioalminates as host materials. For example, Eu 2+ -activated BaAl 2 S 4 attracts attention as a high-luminance blue-emitting phosphor which satisfies requirements for full colour display [2]. Actually, a full colour flat panel display using this phosphor was demonstrated. Therefore, it is supposed that rare-earth-activated alkaline-earth thiogallates and thioalminates are key materials for the designing of inorganic phosphor devices.Investigations of emission and excitation processes are of great importance in phosphor materials. These processes have been well investigated in Ce 3+ -doped CaGa 2 S 4 by using ultraviolet (UV) and visible (VIS) light [3][4][5][6]. The absorption band of Ce 3+ ions locates at 2.92 eV below the fundamental absorption edge of host CaGa 2 S 4 . Two emission bands are observed at 2.65 and 2.40 eV under photoexcitation in the Ce 3+ absorption band, and are attributed to the electronic transitions from the 5d state to the 4f state in Ce 3+ ions. On the other hand, the emission and excitation processes of Ce 3+ ions have not yet been investigated under photoexcitation in the fundamental absorption region. These data are essentially required to know how hot conduction electrons interact with luminescence ions or host materials. Such information would be surely useful for understanding of electroluminescence (EL) and

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Section: Resultsmentioning

confidence: 99%