Luminescence of gadolinium gallium garnet epitaxial films under excitation by synchrotron radiation

The luminescence excited by synchrotron radiation in gadolinium gallium garnet single-crystal films grown by liquid-phase epitaxy from lead-and bismuth-containing solution melts on Gd₃Ga₅O₁₂ substrates is investigated. It is shown that the luminescence intensity in the visible range of the spectrum depends on the type and concentration of impurity ions passing from the solvent into the film.     

Electrical transport properties of gadolinium scandium gallium garnet

Electrical conductivity and thermoelectric power are measured on a single crystal of Gd_3.0Sc_1.8Ga_3.2O₁₂ (GSGG) between 1273 and 1673 K. The measurements are made both in air and in controlled atmospheres, and P_O2 varies from 10^?1.68 to 10^?5.6 MPa. The data indicate GSGG may well be a mixed conductor in this temperature and P_O2 range, with n-type electronic conductivity and ionic transport on the oxygen sublattice. Changes in temperature induce long-lived disequilibrium in electrical conductivity of GSGG (over 30 h at T < 1373 K) that can be explained by temperature dependent cation redistribution. The effective activation energy for equilibrium electrical conductivity is E_a = 2.40 ± 0.05 eV, as opposed to values of E_a between 1.8 and 2.2 eV during actual temperature changes. An additional contribution in the equilibrium E_a, due to thermally activated cation redistribution, can account for the higher value seen.     

Solvothermal synthesis and luminescence properties of Tb-doped gadolinium aluminum garnet

Different concentrations of Tb³⁺ ion-doped gadolinium aluminum garnet (GAG) nanophosphors have been synthesized by solvothermal reaction method and sintered at 1300 °C. The XRD patterns confirm that the GAG phosphors sintered at 1300 °C have a garnet structure with single cubic phase. The calculated crystallite size is about 92 nm. The SEM images of the phosphors show the spherical morphology agglomerated with many small particles. The luminescence properties of these phosphors have been carried out by the emission and excitation spectra along with lifetime measurements. The excitation spectra of GAG:Tb³⁺ phosphors consist of three broad bands due to the 4f⁸→4f⁷5d¹ transition and some sharp peaks due to the 4f⁸→4f⁸ transition. The emission spectra of the phosphors reveal two colors, such as blue due to ⁵D₃→⁷F_J transitions and green due to the ⁵D₄→⁷F_J transitions. The dynamics of the phosphors have been investigated by decay curves and the cross-relaxation process and is observed at 0.5 mol% Tb³⁺ concentration.     

Optical absorption in cobalt-containing single-crystal epitaxial films of gadolinium gallium garnets

Cobalt-containing single-crystal garnet films are grown by liquid-phase epitaxy from supercooled PbO-B₂O₃-and Bi₂O₃-B₂O₃-based solution melts on Gd₃Ga₅O₁₂ substrates. It is shown that cobalt in the films is in a trivalent state. Upon introduction of GeO₂ into the initial solution melt, cobalt transforms into a bivalent state. It is revealed that the absorption spectrum of the grown films exhibits two broad bands in the wavelength ranges 450–800 and 900–1800 nm. Each of these bands contains three components. The spin-orbit splitting of the observed bands is determined.     

Electrophysical properties of epitaxial gallium arsenide doped with acceptor impurities

Epitaxial layers of gallium arsenide doped with zinc and cadmium were grown in a chloride vapor-transport system using diethylzinc and dimethylcadmium as the sources of the impurity. We studied the effect of the inlet pressure of the impurities and the growth temperature on the doping level of the layers. We investigated the temperature dependences of the hole concentration and mobility in layers doped with zinc and cadmium up to different levels.V. D. Kuznetsov Siberian Physicotechnical Institute, Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 54–58, February, 1995.     

飞秒光诱导铽镓石榴石晶体中的磁化响应研究

运用时间分辨抽运-探测光谱技术,研究了磁光晶体铽镓石榴石(TGG)在不同椭圆偏振态的飞秒激光脉冲诱导下的极化和磁化响应.研究表明,当仅存在逆法拉第效应时,探测光旋转角信号和椭圆率信号的变化方向与圆偏振抽运光的旋向相关.这是由于圆偏振光在TGG晶体中产生的瞬态有效磁场的方向依赖于圆偏振光的旋向所致.光诱导磁化过程与材料的性质有关,TGG晶体的顺磁特性决定了其自旋弛豫时间为几十飞秒.由于探测光旋转角信号和椭圆率信号的半高全宽均为500 fs左右,加之信号强度随着抽运光脉冲能量密度的增加呈线性增长,表明TGG晶 关键词： 铽镓石榴石晶体 抽运-探测光谱技术 逆法拉第效应     

Electrophysical properties of doped epitaxial CdSe films

The electrophysical properties of epitaxial films of cadmium selenide doped with zinc or gallium are investigated. It is shown that in doped films intercrystalline barriers are absent, and the mechanism of electron scattering is close to the scattering mechanism in single crystals. It is suggested that the removal of the intercrystalline energy barrier is due to localization of part of the activator at intercrystallite boundaries and neutralization of acceptor states in neutral complexes. The difference between the doping effect of zinc and gallium is shown.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 52–56, March, 1977.     

Phosphorescence of a gadolinium gallium garnet single crystal

The phosphorescence of a Gd₃Ga₅O₁₂ single crystal grown by the Czochralski method is discussed. The phosphorescence was excited by UV radiation of a deuterium lamp.     

An investigation on the magneto-optic properties of terbium gallium garnet under high magnetic field

The superexchange interaction on a magnetic ion may be represented by an effective field H_m = $\lambda$M in some paramagnetic materials, here λ is the coefficient of effective field and M = $\chi$H_e with $\chi$ being the magnetic susceptibility and H_e being the applied field. The variation of the equivalent $\lambda_{\chi}$with the dynamic applied field is given and the crystal field-splitting levels of the excited configuration 4f⁷5d¹ of the Tb³⁺ ion are calculated in the Tb₃Ga₅O₁₂. By means of the effective field H_m and the applied field H_e, the Faraday rotation of Tb₃Ga₅O₁₂ at 6 K and 41 K, under the high magnetic field and at 0.63 μm wavelength, are presented. Our calculated results are in agreement with the experimental data.     

Observation of dark dot splitting pattern in terbium gallium garnet

We have observed a new polarisation pattern in terbium gallium garnet which is both laser excited and mechanically stressed. The pattern can be characterized by a splitting from a “one dot” structure to a “two dots” structure. We have found that the new pattern is very sensitive to the orientation and the strength of the external forces applied to the sample. Thanks to this sensitivity and to the image simplicity, this new effect may be used in a vectorial force sensor and actuator. Received: 25 March 1999 / Accepted: 20 April 1999 / Published online: 25 August 1999     

Highly transparent cerium doped gadolinium gallium aluminum garnet ceramic prepared with precursors fabricated by ultrasonic enhanced chemical co-precipitation

Cerium doped gadolinium gallium aluminum garnet (GGAG:Ce) ceramic precursors have been synthesized with an ultrasonic chemical co-precipitation method (UCC) and for comparison with a traditional chemical co-precipitation method (TCC). The effect of ultra-sonication on the morphology of powders and the transmittance of GGAG:Ce ceramics are studied. The results indicate that the UCC method can effectively improve the homogenization and sinterability of GGAG:Ce powders, which contribute to obtain high transparent GGAG ceramic with the highest transmittance of 81%.     

Optical properties of He+-implanted and diamond blade-diced terbium gallium garnet crystal planar and ridge waveguides

Terbium gallium garnet (Tb₃Ga₅O₁₂, TGG) crystal can be used to fabricate various magneto-optical devices due to its optimal Faraday effect. In this work, 400-keV He⁺ ions with a fluence of 6.0×10¹⁶ ions/cm² are irradiated into the TGG crystal for the planar waveguide formation. The precise diamond blade dicing with a rotation speed of 2×10⁴ rpm and a cutting velocity of 0.1 mm/s is performed on the He⁺-implanted TGG planar waveguide for the ridge structure. The dark-mode spectrum of the He⁺-implanted TGG planar waveguide is measured by the prism-coupling method, thereby obtaining the relationship between the reflected light intensity and the effective refractive index. The refractive index profile of the planar waveguide is reconstructed by the reflectivity calculation method. The near-field light intensity distribution of the planar waveguide and the ridge waveguide are recorded by the end-face coupling method. The He⁺-implanted and diamond blade-diced TGG crystal planar and ridge waveguides are promising candidates for integrated magneto-optical devices.     

Spectral luminescence properties of transparent lead fluoride nanoglassceramics doped with erbium ions

Transparent nanoglassceramics has been synthesized based on lead fluoride silicate glass doped with erbium ions. It is shown that heat treatment of lead fluoride silicate glass leads to the formation of nanoscale (16–40 nm) crystalline phase of lead fluoride. X-ray diffraction analysis and measurement of spectral luminescence properties have revealed that the erbium ions enter the crystalline phase of lead fluoride.     

Growth and the luminescence properties of a lutetium gadolinium garnet doped with Ce3+ and Pr3+ ions

Crystals of lutetium gadolinium garnet solid solutions (Lu_{1 − x} Gd _x )Al₅O₁₂ (0 ≤ x ≤ 0.6) doped with Ce³⁺ and Pr³⁺ ions have been prepared by the horizontal directional crystallization method, and their optical and luminescence properties have been investigated. It has been established that the introduction of gadolinium into the lutetium garnet lattice leads to a decrease in the antisite luminescence (Lu_Al centers) in the UV spectral range and to sensitization of the Ce³⁺ ion luminescence. By contrast, the presence of gadolinium results in the quenching of the Pr³⁺ luminescence due to the nonradiative excitation transfer from Pr³⁺ ions to Gd³⁺ ions.