Secondary excitons in alkali halide crystals

Lushchik, A.; Feldbach, E.; Kink, R.; Lushchik, Ch.; Kirm, M.; Martinson, I.

doi:10.1103/physrevb.53.5379

Cited by 80 publications

(58 citation statements)

References 33 publications

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“…For LaBr 3 crystals, the valence band, according to calculations [17], is formed predominantly by the bromine 4p states and has a weak dispersion, whereas the total width of the valence band E v , according to X ray photoelectron spectroscopy and band structure calculations [17], does not exceed 4 eV. For crystals with a narrow valence band and a large effective mass of holes, the threshold energy of the MEE effect, in accordance with modern concepts of the MEE theory [19], should lie just in the region (2-3)E g . Since E v < E g in LaBr 3 , we can assume that the MEE mechanism is realized by means of the generation of secondary electron-hole pairs due to inelastic scattering of hot photoelectrons.…”

Section: Discussion Of the Experimental Resultsmentioning

confidence: 52%

Luminescence of LaBr3: Ce,Hf crystals under photon excitation in the ultraviolet, vacuum ultraviolet, and X-ray ranges

2014

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Abstract-This study has been carried out using synchrotron radiation, time resolved luminescence ultraviolet and vacuum ultraviolet spectroscopy, optical absorption spectroscopy, and thermal activation spectroscopy. It has been found that, in scintillation spectrometric crystals LaBr 3 : Ce,Hf characterized by a low hygroscopicity, along with Ce 3+ centers in regular lattice sites, there are Ce 3+ centers located in the vicinity of the defects of the crystal structure. It has also been found that the studied crystals exhibit photoluminescence (PL) of new point defects responsible for a broad band at wavelengths of 500-600 nm in the PL spectra. The minimum energy of interband transitions in LaBr 3 is estimated as E g ~ 6.2 eV. The effect of multiplication of electronic excitations has been observed in the range of PL excitation energies higher than 13 eV (more than 2E g ). Thermal activation studies have revealed channels of electronic excitation energy transfer to Ce 3+ impurity centers.

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Section: Discussion Of the Experimental Resultsmentioning

confidence: 52%

Luminescence of LaBr3: Ce,Hf crystals under photon excitation in the ultraviolet, vacuum ultraviolet, and X-ray ranges

2014

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“…In general, the structures due to the creation of secondary excitons have also been observed around the multiple of E g in excitation spectra [19,20]. However, such structures are not seen in the excitation spectrum in figure 2, because no sharp peak due to direct excitonic transitions appears in the reflectivity spectrum in figure 1.…”

Section: Discussionmentioning

confidence: 86%

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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“…Используя s 2 -центры, а затем и некоторые редкоземельные и переходные ионы (например, Ce 3+ , Eu 3+ , Tb 3+ , Mn 2+ , Cr 3+ ), были изучены особенности собственных электронных возбуждений в широкощелевых галогенидах и оксидах металлов. Удалось также обнаружить и подробно исследовать основные механизмы размножения электронных возбуждений и фотонного умножения, когда поглощение одного фотона ведет к образованию двух электронно-дырочных (e-h) пар [5,6]; e-h пары и экситона [6,7]; прямому возбуждению горячим электроном проводимости центра люминесценции (аналог механизма Франка-Герца в газах) [8,9]; а также получению трех e-h пар при ионизации фотоном электрона из более глубокой, чем валентная (np 6 ), электронной оболочки ns 2 [10].…”

Section: аннотацияunclassified

Low-temperature investigation of electronic excitations in wide-gap materials doped with RE3+ or Cr3+ ions

Lushchik

Kudryavtseva

et al. 2011

Opt. Spectrosc.

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Secondary excitons in alkali halide crystals

Cited by 80 publications

References 33 publications

Luminescence of LaBr3: Ce,Hf crystals under photon excitation in the ultraviolet, vacuum ultraviolet, and X-ray ranges

Luminescence of LaBr3: Ce,Hf crystals under photon excitation in the ultraviolet, vacuum ultraviolet, and X-ray ranges

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

Low-temperature investigation of electronic excitations in wide-gap materials doped with RE3+ or Cr3+ ions

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