Akimasa Ohnishi

Probing shallow electron traps in cerium-doped Gd3Al2Ga3O12 scintillators by UV-induced absorption spectroscopy

From measuring absorption spectra of cerium-doped Gd3Al2Ga3O12 (Ce:GAGG) and undoped GAGG crystals at low temperatures under UV-light irradiation, we find that they exhibit a broad band at around 12000 cm−1. This band is enhanced by high-temperature annealing under a hydrogen atmosphere. On the basis of present experimental results, the UV-induced band is assigned to shallow electron traps of defect complexes associated with oxygen vacancies. The UV-induced band completely disappears with Mg2+ codoping. We conclude that the Mg2+ codoping has the effect of inhibiting the formation of shallow electron traps, which realizes a faster scintillation response of Ce:GAGG.

Topological phase transitions driven by magnetic phase transitions in Fe(x)Bi2Te3 (0≤x≤0.1) single crystals.

We propose a phase diagram for Fe(x)Bi2Te3 (0≤x≤0.1) single crystals, which belong to a class of magnetically bulk-doped topological insulators. The evolution of magnetic correlations from ferromagnetic to antiferromagnetic gives rise to topological phase transitions, where the paramagnetic topological insulator of Bi2Te3 turns into a band insulator with ferromagnetic-cluster glassy behavior around x∼0.025, and it further evolves to a topological insulator with valence-bond glassy behavior, which spans over the region from x∼0.03 up to x∼0.1. This phase diagram is verified by measuring magnetization, magnetotransport, and angle-resolved photoemission spectra with theoretical discussions.

Fabrication of Zn1-xMgxO Fine Bulk Crystals and Nanocrystals by Complex Decomposition Method and Their Characterization

Zn1-xMgxO fine bulk crystals with Mg contents of x = 0–0.15 are fabricated by a complex decomposition method, in which starting complexes of Zn1-xMgx(C2O4)2H2O hetero metal coordination polymers, synthesized with [Zn(C2O4)2(H2O)2]2- dioxalato complex ions, are decomposed at a relatively low temperature in air. Their structural and optical characterizations are carried out by X-ray powder diffraction and diffuse reflection measurements, respectively. Zn1-xMgxO nanocrystals with x = 0–0.10 are also fabricated by the thermal decomposition of Zn1-xMgx(C2O4)2H2O coordination-polymer nanocrystals synthesized with dioxalato complex ions inside reverse micelles. Samples are characterized by optical absorption measurements.

Sondheimer oscillation as a signature of surface Dirac fermions

Topological states of matter challenge the paradigm of symmetry breaking, characterized by gapless boundary modes and protected by the topological property of the ground state. Recently, angle-resolved photoemission spectroscopy (ARPES) has revealed that semiconductors of Bi

Thermal Stability of Photostimulated Luminescence Centers in BaFBr and BaFBr:Eu2+ Single Crystals

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Determination of optical gain of self-trapped exciton luminescence in CdI2

Se

Time-resolved photoluminescence spectroscopy of Ce:Gd3Al2Ga3O12 crystals

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Energy location of Ce3+ 4f level and majority carrier type in Gd3Al2Ga3O12:Ce crystals studied by surface photovoltage spectroscopy

and Bi

Electronic Structure and Auger-Free Luminescence in Cs2ZnCl4 Crystals

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Valence electronic states of p-type β-FeSi2 single crystal studied by high-resolution and resonant photoelectron spectroscopy

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