Conventional Czochralski Technique Research Articles

Crystal growth, luminescence, and scintillation properties of Zn2Te3O8 crystal for 0νββ decay search

A single crystal of Zn2Te3O8 (ZTO) was grown using the conventional Czochralski technique.

Luminescence and Scintillation Characterization of Sodium-Based Tungstate (Na2W2O7) Crystal for Dark Matter Search

A Na <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> W <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> single crystal was grown with a conventional Czochralski technique in a platinum crucible. A solid-state reaction method was used for the preparation of the polycrystalline compound. Temperature-dependent luminescence and scintillation properties of the crystal were studied under the excitation with a 280 nm UV light-emitting diode (LED) source, an X-ray source, and a <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">90</sup> Sr (beta) source. At different temperatures (from 300 to 10 K), an as-grown crystal’s luminescence and scintillation light output was compared with a CaMoO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> crystal. Although the light output of Na <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> W <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> crystal at room temperature is lower than CaMoO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> crystal, at 10 K, it is almost comparable. Compared to room temperature, the crystal’s luminescence and scintillation light output at 10 K were increased by ~17 and ~14 fold, respectively. The decay time of the crystal was studied between 300 to 10 K using a 280 nm LED excitation source, and it varies from 3 (300 K) to ~94 μs (10 K). A thermoluminescence (TL) study was carried out between 10 to 550 K. The kinetic parameters of the TL peaks are calculated with various standard methods. The current result suggests that the studied crystal has good potential as a cryogenic detector for dark matter search experiments in the near future.

Growth, optical, and luminescence characterization of LiCsMoO4 crystal

A crack-free LiCsMoO4 crystal was grown with the conventional Czochralski technique. The optical properties of the crystal show it transparent well in the visible region. The luminescence properties of the crystal were studied from 300 to 14 K under the excitation with a 280 nm light-emitting diode (LED). At room temperature, the luminescence light yield is low; however, it increases significantly at low temperatures. The decay time of the crystal is measured under the excitation of the crystal with the 280 nm LED source. The decay times at all the temperatures are fitted with three exponential functions. The average decay time from 300 to 14 K varies from 6.7 to 8.6 μs. A thermoluminescence (TL) study of the crystal was carried out from 9 to 300 K. Three TL peaks are found between 165 and 250 K. This study shows that the developed crystal has a potential application in search of neutrinoless double-beta decay of 100Mo at cryogenic temperatures.

Hf 4+ Ion Concentration Dependence of Holographic Storage Properties in Hf:Fe:Cu:LiNbO3 Crystals

AbstractA series of Hf:Fe:Cu:LiNbO3 crystal with various concentrations of Hf 4+ ion doping are grown in air by the conventional Czochralski technique. The segregation coefficients of the Hf 4+, Fe3+, and Cu2+ ions in the crystals are carried out with an inductively coupled plasma‐atomic emission spectrometer. The birefringence gradient method is measured in order to analyze the optical homogeneity of Hf:Fe:Cu:LiNbO3 crystals. The holographic storage properties of Hf:Fe:Cu:LiNbO3 crystals are investigated by the two‐wavelength coupling experiment. The result shows that the writing time constant shortens from 529.3 to 214.4 s, and the dynamic range increases from 1.12 to 8.07 with increasing Hf 4+ content in the Hf:Fe:Cu:LiNbO3 crystals.

Growth, Luminescence and Scintillation Characterization of Disodium Di-tungstate (Na2W2O7) Crystal Scintillator

A single crystal of Na2W2O7 was grown by using the conventional Czochralski technique. The crystal structure of the grown sample was verified by using a powder X-ray diffraction (XRD) analysis. The luminescence, as well as scintillation, properties of the crystals were evaluated at room temperature. The emission spectra of the crystal were obtained by irradiating the sample with X-ray and proton sources. The trap level of the grown crystal was studied from 325 K to 500 K, and different kinematic parameters were calculated. The scintillation properties such as; energy resolution, light yield, fluorescence decay time and α/β ratio of the crystal, were studied by using γ- (662 keV from 137Cs) and α- (5.4 MeV from 241Am) sources. The luminescence and the scintillation results revealed that the Na2W2O7 crystal would be a good material for the dark matter search and for high-energy physics experiment.

Luminescence and low temperature trap centers in mixed rare earth borate crystal

The single crystal of this compound has been grown from melt by using a conventional Czochralski technique. The temperature dependent luminescence spectra were measured using a 265 nm laser as an exciting source in the range of 10–300 K. The scintillation decay time profile was measured and found to have three components. The influence of the trap centers on the luminescence properties was studied by means of thermoluminescence (TL) glow peak analysis. Low temperature TL glow peaks were measured in the temperature range of 10–300 K at the heating rate of 0.1 K/s for X-ray irradiated sample. The TL glow peak consists of two dominant peaks at 88 and 109 K. Several glow peaks with a complex nature causes the decrease in the light yield at temperatures below 250 K, and along with long scintillation decay components were observed. The trap parameters such as activation energy (E), frequency factor (s) and order of kinetics (b) were calculated using various standard methods such as peak shape (PS), variable heating rate (VHR), initial rise (IR) and computerized glow curve deconvolution (CGCD).

Dopant occupancy and exposure energy in Hf:Nd:LiNbO3 crystal as a function of [Li]/[Nb] ratios

A series of Hf: Nd: LiNbO3 crystals with various [Li]/[Nb] ratios ([Li]/[Nb] = 0.94, 1.05, 1.20, 1.38) in the melt were grown by conventional Czochralski technique. The distribution coefficients of Hf4+ and Nd3+ ions were recorded by an inductively coupled plasma-atomic emission spectrometer (ICP-AES). The effective distribution coefficient of Hf4+ is reduced and that of Nd3+ is increased with the increase of [Li]/[Nb] ratio in the melts. In all cases, the effective distribution coefficients is less than 1. The IR transmission spectroscopy of the Hf: Nd: LiNbO3 crystals were measured, getting the results that Hf: Yb: Ho: LiNbO3 crystals with 1.05 [Li]/[Nb] ratios was the stoichiometric. The optical damage resistance ability of Hf:Nd:LiNbO3 crystals were studied by light-induced scattering exposure energy flux threshold method and it increases with the increasing of [Li]/[Nb] ratios. When the [Li]/[Nb] ratio is 1.38 in the melt (the sample 4#), the exposure energy achieves 687.35 J/cm2, approximately 441 folds than that of the sample 1# ([Li]/[Nb] = 0.94) in magnitude.

Effects of aluminum substitution on the structure and electric properties of langasite family crystals

The effects of aluminum substitution on the structure and electric properties of langasite (La3Ga5SiO14) family crystals are reported. The maximum Al content x of La3Ga5-xAlxSiO14 (LGAS), La3Nb0.5Ga5.5-xAlxO14 (LNGA), and La3Ta0.5Ga5.5-xAlxO14 (LTGA) crystals grown by the conventional Czochralski technique are x = 0.9, 0.2, and 0.5, respectively. Single-crystal X-ray structural analysis reveals that Al atoms are distributed in all cation sites except for the decahedral one occupied by La, rather than favoring the smallest tetrahedral sites. The electrical properties of the Al-substituted crystals were also compared with those of pure ones. Al substitution was found to affect the piezoelectric constant d14, but not d11. The LGAS and LTGA crystals exhibit higher electric resistivity ρ as a result of Al substitution. Among the Al-substituted and pure crystals, the LTGA crystal featured the lowest temperature dependence of d11 and highest ρ, making it the most suitable of the group for high-temperature piezoelectric applications.

Effect of dopant concentration on the spectroscopic properties in an In3+ doped (0, 1, 2 and 4 mol%) Yb:Tm:LiNbO3 crystal

A series of Yb:Tm:LiNbO3 crystals with x mol% In3+ ions (x = 0, 1,2 and 4 mol%) were grown by a conventional Czochralski technique for the first time.

The effect of In3+ doping on the optical characteristics of Ho:LiNbO3 crystals

A series of Ho:LiNbO3 crystals doped with x mol% In3+ ions (x=0, 1, 3 and 5mol%) were grown by the conventional Czochralski technique. Up-conversion emission spectra was observed under 808nm femtosecond laser excitation in the In3+ doped Ho:LiNbO3 crystals at room temperature. The experimental results indicate that blue, green, violet and red up-conversion emission can be obtained from In3+ doped Ho:LiNbO3 crystals. From the pump energy dependence investigation, it is known that the up-conversion mechanism is the two-photon process. The light-induced scattering was investigated as a function of exposure energy. The effect of In3+ on the optical characteristics of Ho3+ in LiNbO3 crystal was investigated and concluded, and is reported here. The surface the as-prepared In3+ doped Ho:LiNbO3 is very smooth and practically free of droplets as highlighted by atomic force microscopy (AFM). The root-mean-square (rms) surface roughness of the sample was determined to be 11.573nm.

Investigation on the OH^− absorption and blue photorefractive properties in Zr:Ru:Fe:LiNbO_3 crystals as a function of Li composition

A series of ZrO2-doped Ru:Fe:LiNbO3 crystals with various Li composition were grown by conventional Czochralski technique. The OH− absorption spectra were measured, and the Lorentzian fitting was employed to analyze the defect structures. The photorefractive properties in these crystals were investigated as a function of Li/Nb ratios. The recording sensitivity of Li-enriched Zr:Ru:Fe:liNbO3 crystal was 1.70 cm/J, and the diffraction efficiency was as high as 44.3%, while this crystal could withstand a laser intensity of 3.4×104 W/cm2 at 476 nm irradiation. Experimental results definitely showed that Zr:Ru:Fe:LiNbO3 crystals were promising blue photorefraction materials for holographic volume storage.

Optical properties of Sr3NbGa3Si2O14 crystal

Single crystal of Sr3NbGa3Si2O14 was successfully grown using the conventional Czochralski technique. UV–VIS–NIR spectrometry and spectroscopic ellipsometry have been used to study the optical properties of SNGS crystal. From the transmission spectrum, the cut-off wavelength is determined to be 284nm. Refractive indices of SNGS crystal were accurately determined in the wavelength region between 350nm and 800nm, based on the analysis of the transmission spectrum and SE measurements at multiple angles of incidence. The effects of varied values of k on no and ne were also discussed. Furthermore, the phase matching angle of SNGS crystal is 39.00°.

Influence of Li and Nb ratios on the defect structure and exposure energy in LiNbO 3:Fe:Mn:Zr crystals

A series of LiNbO 3:Fe:Mn:Zr crystals with different ratios of Li/Nb in the melt (0.94,1.05,1.20 and 1.38, respectively) were grown by the conventional Czochralski technique. The ultraviolet–visible spectra were measured in order to analyze the defect structure of the crystals. The measurement of the Zr concentrations and Li/Nb ratios in the crystals was carried out with an inductively coupled plasma atomic emission spectrometer. The light-induced scattering was investigated as a function of exposure energy. The results showed that the ability to resist the light-induced scattering was improved considerably with the increase of the Li/Nb ratio. The relationship between the defect structures and the light-induced scattering was discussed.

Crystal growth, VTE treatment, and characterizations of Nd-doped LiTaO3

Congruent 0.2 and 0.5mol% Nd-doped LiTaO3 single crystals were grown by the conventional Czochralski technique. Near-stoichiometric lithium-tantalate wafers were also produced from these crystals by the vapor-transport equilibration (VTE) process. The crystals were characterized by the measurements of composition (by inductively coupled plasma atomic emission spectroscopy (ICP-AES)), UV absorption edge, Curie temperature, and thermal diffusivity. From the ICP-AES study, we found that Li/Ta ratio increased by the VTE treatment, while Nd/Ta ratio was found to decrease with crystal length. Blue-shift in the absorption edge was observed in the VTE treated crystals as compared with the congruent ones. The Curie temperature decreased with increasing Nd concentration, while thermal diffusivity was found to increase after the VTE treatment.

Crystal growth and characterization of LuAG:Ce:Tb scintillator

To investigate the possibility of Tb 3+→Ce 3+energy transfer, we grew single crystals of Lu 3Al 5O 12:Ce co-doped with Tb 3+ using both the micro-pulling-down method and the conventional Czochralski technique. Compositional and phase homogeneity, growth defects, and crystallographic properties were studied. Visible non-uniformity of dopants distribution in the radial direction was observed in the micro-pulling-down grown crystals. Underlying luminescence processes were evaluated by measuring luminescence properties under photo-, X- and gamma-rays excitation at room temperature.

Reduction of grown-in dislocation density in Ge Czochralski-grown from the B 2O 3-partially-covered melt

Germanium (Ge) single crystals with an extremely low density of grown-in dislocations were grown by the Czochralski (CZ) technique with boron oxide (B 2O 3) liquid. Because attachment of particles floating on the melt surface to a growing Ge crystal leads to generation of dislocations during the growth, partial covering of the Ge melt surface with B 2O 3 liquid was attempted. Such attachment of particles was drastically suppressed or the particles were caught by the introduction of B 2O 3 liquid, and a particle-free Ge melt was realized in the central region of the melt surface. Ge single crystals were successfully grown from such melt, the grown-in dislocation density being 0–1×10 3 cm −2, which was remarkably lower than that in Ge crystals grown by a conventional CZ technique. The contaminations by B and O atoms of the grown crystal detected by SIMS analysis were very low. These Ge crystals have the potential for application to be applied as high-quality, dislocation-free substrates of GaAs solar cells for various usages including in space.

Growth and study of nonlinear refraction and absorption in Mg doped [formula omitted] single crystals

Undoped, 5 and 7 mol % MgO doped LiNbO 3 single crystals were grown by conventional Czochralski technique. Comparative study of the nonlinear refractive index and nonlinear absorption coefficient in these crystals was undertaken using Z-scan technique. We have also calculated real and imaginary parts of the third-order nonlinear susceptibility using experimentally obtained values of nonlinear refractive index and nonlinear absorption coefficient. We found the change in sign of the real part of the susceptibility by doping the LiNbO 3 crystal while the imaginary part of susceptibility is found to minimize at 5 mol % doping concentration. The absolute values of the third-order susceptibility decreases with increasing doping concentration.

Dielectric, elastic and piezoelectric properties of RCa 4O(BO 3) 3 ( R=rare-earth elements) crystals with monoclinic structure of point group m

Rare-earth calcium oxoborate RCa 4O(BO 3) 3 ( R=La, Gd, Y) piezoelectric single crystals were successfully grown by a conventional RF-heating Czochralski (Cz) technique. They belong to the monoclinic system with point group m, and have 27 independent material constants. We developed the determination scheme (cuts and vibration modes) of the material constants in point group m. Their material constants were evaluated on the basis of the determination scheme and systematically compared. Also, the Rayleigh surface acoustic wave (RSAW) velocities v and coupling factors K 2 for the fundamental X-, Y- and Z-cuts were theoretically simulated in their crystals by Campbell and Jones's method, which showed a good agreement with the measured values. Moreover, from the calculated result in their all propagation direction, it was confirmed that (180°, 120°, 167°)-cut of the RCa 4O(BO 3) 3 ( R=Y) and (180°, 146°, 167°)-cut of the RCa 4O(BO 3) 3 ( R=La), indicated excellent RSAW propagation properties when compared with existing piezoelectric crystals.

Influence of Nd:Zn codoping in near-stoichiometric lithium niobate

Near-stoichiometric lithium niobate (SLN) crystals doped with up to 1.6 mol % Zn and codoped with various Nd concentrations in the melt (0.2, 0.5, 0.9, and 1.5 mol %) (Nd:Zn:SLN) are grown from 58.6 mol % Li(2)O using conventional Czochralski technique. Crystals are pulled at the rate of 0.35 mmh with seed rotation at 9 rpm. Concentrations of Zn and Nd in the crystal are varied by adding appropriate amounts of ZnO and Nd(2)O(3) to the starting composition. Unit cell parameters of the grown crystals are calculated by Rietveld refinement method using FULLPROFF software. Domain structure studies are carried out by chemical etching followed by microscopic examination. Dielectric studies reveal the existence of piezoelectric resonance at high frequencies. Enhancement in dielectric constant and tan delta in Nd doped samples has been attributed to the space charge polarization. Nd doped samples exhibit reduction in the relative permittivity after oxygen annealing. Transmission spectra of Nd:Zn:SLN crystals in the UV region exhibit blueshift in the cutoff wavelength. In Mid Infrared (MIR) region crystals doped with 1.6 mol % Zn have shift in the OH absorption peak from 2873 to 2833 nm. Judd-Ofelt analysis carried out on the absorption spectra of codoped crystal yields the lifetime of 104 mus for the metastable state (4)F(32). The branching ratio for the electronic transition from (4)F(32) to (4)I(112) is high compared to that for (4)F(32) to (4)I(132), indicating a higher emission cross section for the former transition. Laser damage threshold evaluated using 532 nm, 5 ns pulsed neodymium doped yttrium aluminum garnet laser, shows an increase by two orders of magnitude for crystals doped with 1.6 mol % Zn. Photorefractive damage threshold for these crystals shows an enhancement of four orders of magnitude due to increase in the photoconductivity.

Properties of rare-earth scandate single crystals (Re=Nd−Dy)

Rare-earth (RE) scandate single crystals ranging from NdScO 3 to DyScO 3 were grown by the conventional Czochralski technique. The crystals were found to have a non-stoichiometric composition caused by RE-deficiency on the A-site of the distorted perovskite structure. Their pseudocubic lattice constants lie between 3.95 and 4.01 Å and their average thermal expansion coefficients are between 8.2×10 −6 and 10.9×10 −6 K −1. The pseudocubic lattice constants of the RE scandates vary in about 0.01 Å steps as the RE series is traversed, enabling the growth of substrates appropriate for the strain engineering of perovskite thin films. The crystalline perfection and homogeneity of the DyScO 3 and GdScO 3 single crystals are characterized by a full-width at half-maximum of the 220 reflection of the substrates of about 20–25 arcsec in ω and a very small fluctuation margin of about ±3 arcsec over the whole wafer surface. The average dislocation density of the RE scandate crystals was 10 3–10 5 cm −2. These characteristics make RE scandate single crystals some of the best available substrates for the epitaxial growth of perovskite thin films.