Composite substrate LiGaO2(001)/beta-Ga2O3(100) fabricated by vapor transport equilibration

Highly (001) orientation LiGaO2 layers have been successfully fabricated on (100) beta-Ga2O3 surface by vapor transport equilibration (VTE) technique. The temperature is very important for the WE treatment. At low temperature (800 degrees C), LiGaO(2)layers are textured. As the temperature was raised to 1100 C the layer becomes highly oriented in the [100] direction. It shows that the best temperature for WE treatment is 1100 degrees C. This technique is promising to fabricate small lattice mismatch composite substrate of LiGaO2 (001)//beta-Ga2O3 (100) for GaN films. (c) 2006 Elsevier B.V. All rights reserved.

Fabrication of beta-BaB2O4 layers on (001) Sr2+-doped alpha-BaB2O4 by vapor transport equilibration (VTE)

Crystalline beta-BBO layers have been successfully prepared on (0 0 1)-oriented Sr2+-doped alpha-BBO substrates using vapor transport equilibration technique. The layers were characterized by X-ray diffraction, X-ray rocking curve and transmission spectra. The present results manifest that the VTE treatment time and powder ratio are important factors on the preparation of beta-BBO layers. beta-BBO layers with a highly (0 0 l) preferred orientation were obtained according to XRD profiles. The full width at half-maximum of the rocking curve for the layer is as low as about 1000 in., which shows the high crystallinity of the layer. These results reveal the possibility of fabricating beta-BBO (0 0 1) layers on (0 0 1)-oriented Sr2+-doped alpha-BBO substrates by VTE. (C) 2006 Elsevier Ltd. All rights reserved.

Defects in LPE-grown beta-barium borate (beta-BaB2O4) thin films

Morphological defects in beta-barium borate (beta-BBO) thin films grown on Sr2+ -doped alpha-BBO substrates by liquid phase epitaxy (LPE) technique were studied by scanning electron micrograph (SEM), atomic force microscopy (AFM) and optical spectroscopy. The present results indicate that the main defects exit in beta-BBO thin films are microcracks and hollow structure. The formation of microcrack is due to the lattice mismatch and the difference of thermal expansion coefficients between substrate and film. The hollow structure might be caused during the combination of islands, which formed in the initial stage. (C) 2006 Elsevier GmbH. All rights reserved.

Single crystal beta-Ga2O3: Cr grown by floating zone technique and its optical properties

beta-Ga2O3: Cr single crystals were grown by floating zone technique. Absorption spectra and fluorescence spectra were measured at room temperature. The values of field splitting parameter Dq and Racah parameter B were obtained by the peak values of absorption spectra. The value 10Dq/B=23.14 manifests that in beta-Ga2O3 crystals Cr3+ ions are influenced by low energy crystal field. After high temperature annealing in air, the Cr3+ intrinsic emission was enhanced and the green luminescence disappeared. The strong and broad 691 nm emission was obtained at 420 nm excitation due to the electron transition occurred from T-4(2) to (4)A(2). The studies manifest that the beta-Ga2O3 crystals have the potential application for tunable laser.

Demonstration of GaN/InGaN light emitting diodes on (100) beta-Ga2O3 substrates by metalorganic chemical vapour deposition

The growth and fabrication of GaN/InGaN multiple quantum well (MQW) light emitting diodes ( LEDs) on ( 100) beta-Ga2O3 single crystal substrates by metal-organic chemical vapour deposition (MOCVD) technique are reported. x-ray diffraction (XRD) theta-2 theta. scan spectroscopy is carried out on the GaN buffer layer grown on a ( 100) beta-Ga2O3 substrate. The spectrum presents several sharp peaks corresponding to the ( 100) beta-Ga2O3 and ( 004) GaN. High-quality ( 0002) GaN material is obtained. The emission characteristics of the GaN/InGaN MQW LED are measurement. The first green LED on beta-Ga2O3 with vertical current injection is demonstrated.

The separation of beta-BBO phase in alpha-BBO crystal by the irradiation of femtosecond laser

We observed and described some phenomena, which were that when a alpha-BBO crystal was irradiated by a focused femtosecond laser beam, the temperature effect happened in a minute area of focus, then the induced beta-BBO phase was separated within the minute area in the alpha-BBO crystal. (C) 2007 Elsevier B.V. All rights reserved.

Studies of magnetic interactions in Mn-doped β-Ga2O3 from first-principles calculations

The magnetic behavior of Mn-doped beta-Ga2O3 is Studied from first-principles calculations within the generalized gradient approximation method. Calculations show that ferromagnetic ordering is always favorable for configurations in which two Mn ions substitute either tetrahedral or octahedral sites, and the ferromagnetic ground state is also sometimes favorable for configurations where one Mn ion substitutes a tetrahedral site and another Mn ion substitutes an octahedral site. However, the configurations of the latter case are less stable than those of the former. (c) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

17 beta-Estradiol and progesterone improve in-vitro cytoplasmic maturation of oocytes from unstimulated prepubertal and adult rhesus monkeys

BACKGROUND: Effects of 17beta-estradiol and progesterone on rhesus monkey oocyte maturation in vitro were evaluated by embryo development subsequent to IVF. METHODS AND RESULTS: In experiment 1, immature cumulus-oocyte complexes collected from unstimulated adult females during the non-breeding season were matured in modified medium CMRL-1066 containing various combinations of gonadotrophins (FSH + LH), estradiol and/or progesterone. Formation of morulae and blastocysts was greatest in oocytes matured in medium containing estradiol and/or progesterone, with or without gonadotrophins (morula 38-46%, blastocyst 14-20%) than in control oocytes matured without estradiol or progesterone (morula 14%, blastocyst 0%). In experiment 2, cumulus-oocyte complexes from unstimulated prepubertal female monkeys were matured in medium with gonadotrophins, estradiol or progesterone. The best development to the morula stage was obtained with oocytes matured with gonadotrophins and estradiol or gonadotrophins and progesterone (43 and 25 morulae, respectively), while control oocytes matured with gonadotrophins but without steroid hormones gave the poorest morula developmental response (12%). However, there was no difference in blastocyst development across all groups (0-3%). CONCLUSIONS: These results demonstrate that during rhesus monkey oocyte maturation in vitro: (i) estradiol or progesterone can improve oocyte developmental competence; (ii) immature oocytes from prepubertal versus adult females have differential responses to challenge with estradiol or progesterone.

beta gamma-CAT, a non-lens beta gamma-crystallin and trefoil factor complex from amphibian skin secretions, caused endothelium-dependent myocardial depression in isolated rabbit hearts

Previous in vivo study demonstrated that beta gamma-CAT, a newly identified non-lens beta gamma-crystallin and trefoil factor complex from frog Bombina maxima skin secretions, possessed potent lethal toxicity on mammals resulted from hypotension and cardi