Growth, characterization and optical quality of CaF2 single crystals grown by the temperature gradient technique

The CaF2 single crystals with diameters up to 200 mm were successfully grown by modified temperature gradient technique (TGT), which are suitable for application as optical elements in the ultraviolet range. The optimizations of various growth parameters were systematically studied. Properties of as-grown CaF2 crystals were characterized by the nature of inclusions, dislocations, crystallinity, and impurities contents. The results showed that the dislocations and multinucleation were mostly constrained in the conical part of the crystals with the cylindrical parts having the best crystalline quality and lowest impurity contents. The high optical quality of TGT-grown CaF2 single crystals was also confirmed to have excellent optical transmission in 190-2500 nm and refractive index homogeneity. (c) 2005 Elsevier Ltd. All rights reserved.

Crystal growth and spectroscopic characterization of Yb-doped and Yb, Na-codoped CaF2 laser crystals by TGT

High-quality 2at%-doped Yb:CaF2 and Yb,Na:CaF2 single crystals with diameter of 76mm were grown by the temperature gradient technique. For the first time, distribution coefficients (KO) of Yb in the two crystals were determined to be 1.07 and 0.91, respectively, by measuring the Yb concentrations at the growth starting position in the as-grown boules. Absorption and emission spectra of the two different crystals were measured at room temperature. Experimental results show that Na+ ions codoping with Yb3+ as charge compensators make Yb3+ ions in CaF2 lattice to be a quasi-single-center system, and greatly suppress the deoxidization of Yb3+ to Yb2+ (c) 2005 Elsevier B.V. All rights reserved.

Crystal growth and optical properties of Gd1.99-xYxCe.0.01SiO5 single crystals

Gd1.99-xYxCe0.01SiO5 (Ce:GYSO) crystals (x = 0, 0.0995, 0.199) have been grown by the Czochralski (Cz) method. Crystal structure and the distribution coefficients of Ce have been determined for all three crystals. Spectroscopic measurements indicate that optical transmittance and luminescence intensity of Gd1.99-xYxCe0.01SiO5 (x = 0.0995, 0.199) crystals are Substantially higher than those of Ce:Gd2SiO5 (Ce:GSO), especially at x = 0.0995, which makes them good candidate materials for scintillation applications. The particularly important result is that the alloyed Ce:GYSO crystals can be grown easily by the Cz method and, unlike Ce:GSO, they do not undergo cleavage during the growth process or subsequent mechanical treatment. (c) 2005 Elsevier B.V. All rights reserved.

Growth and characterization of new transparent conductive oxides single crystals beta-Ga2O(3): Sn

Tin oxide doped beta-Ga2O3 single crystals are recognized as transparent conductive oxides (TCOs) materials. They have a larger band gap (4.8 eV) than any other TCOs, thus can be transparent in UV region. This property shows that they have the potential to make the optoelectronic device used in even shorter wavelength than usual TCOs. beta-Ga2O3 single crystals doped with different Sn4+ concentrations were grown by the floating zone technique. Their optical properties and electrical conductivities were systematically studied. It has been found that their conductivities and optical properties were influenced by the Sn4+ concentrations and annealing. (c) 2006 Elsevier Ltd. All rights reserved.

Growth and spectral characterization of beta-Ga2O3 single crystals

Beta gallium oxide (beta-Ga2O3) single crystals were grown by the floating zone technique. The absorption spectra and the luminescence of the crystals were measured. The absorption spectra showed an intrinsic short cutoff edge around 260 nm with two shoulders at 270 and 300 nm. Not only the characteristic UV (395 nm), blue (471 nm) and green (559 nm) lights, but also the red (692 nm) light can be seen in the emission spectra. The deep UV light was attributed to the existing of quantum wells above the valence band and the red light was owed to the electron-hole recombination via the vicinity donors and acceptors. (c) 2006 Elsevier Ltd. All rights reserved.

Hydrothermal growth and characterization of ZnO crystals

ZnO crystals with dimensions of 30 x 38 x 8 turn 3 have been grown by the hydrothermal method using a mixed solution of KOH, LiOH and H2O2. The growing rates for +c(0001) and -c(000 (1) over bar) were 0.17 and 0.09 mm/day, respectively. The crystal color was very light green for +c sector and dark brown for -c sector. For the +c sector, the resistivity at room temperature was 80 0 cm, the carrier concentration was about 10(4)/cm(3), and the mobility was about 100 cm(2)/Vs. The full-width at half-maximum (FWHM) of double axis X-ray rocking curve for the polished Zn face cut from +c sector was 45 arcsec. The photoluminescence (PL) spectrum and the absorption spectrum of +c part of the crystals at room temperature were also reported and discussed in this paper. (c) 2008 Elsevier B.V. All rights reserved.

Growth of large sized y Ba 2Cu 3O 7 single crystals using the top seeded melt growth process

Neutron scattering experiments are fundamental to the study of magnetic order and related phenomena in a range of superconducting and magnetic materials. Traditional methods of crystal growth, however, do not yield single crystals of sufficient size for practical neutron scattering measurements. In this paper, we demonstrate the growth of relatively pure, large Y Ba 2Cu 3O 7 single crystals up to 30mm in diameter using a top seeded melt growth process. The characterization of the microstructural and magnetic properties of these crystals indicates that they contain <2% of impurity phases and, hence, exhibit only weak flux pinning behaviour. © 2012 IOP Publishing Ltd.