• Korean Journal of Crystallography
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• v.1 no.1
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• pp.29-34
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• 1990

Single crystals of the peritectic compound MgTiO3 up to 8 m diameter and 100mm long along the [1010] axis. were yon by the travelling solvent floating zone technique using a halogen lamp image furnace. The grown single crystal. which shows a solid solution range at high temperature, exsolves TiO2 component if it is annealed very slowly to room termperature. Grown boules were black but become translucent with pinkish brown color after tempering at 1100 t for 8-10 hours in oxygen atmosphere and showed distint chatoyancy along the (0001) plane. The grown crystal can be used as a new modified cat's eye gemstone. The optimum conditions were as follows ;Sintering temperature of the charge rod, 1300℃ the growth rate, 2-2.5mmh and the composition of the charge rod in molar ratio. MgO : TiO2 : 1:1.05.

• Journal of the Korean Ceramic Society
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• v.55 no.2
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• pp.108-115
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• 2018

The increasing demands for three-dimensional (3D) electronic and optoelectronic devices have triggered interest in epitaxial growth of 3D semiconductor materials. However, most of the epitaxially-grown nano- and micro-structures available so far are limited to certain forms of crystal arrays, and the level of control is still very low. In this review, we describe our latest progress in 3D epitaxy of oxide and nitride semiconductor crystals. This paper covers issues ranging from (i) low-temperature solution-phase synthesis of a well-regulated array of ZnO single crystals to (ii) systematic control of the axial and lateral growth rate correlated to the diameter and interspacing of nanocrystals, as well as the concentration of additional ion additives. In addition, the critical aspects in the heteroepitaxial growth of GaN and InGaN multilayers on these ZnO nanocrystal templates are discussed to address its application to a 3D light emitting diode array.

• Bulletin of the Korean Chemical Society
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• v.16 no.7
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• pp.588-591
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• 1995

Single crystals of (ZnSe)1-x(CuMSe2)x (M=Al, Ga, or In) were grown by chemical vapor transport technique. Powdered polycrystalline samples of (ZnSe)1-x(CuMSe2)x (M=Al, Ga, or In) were also prepared by the direct combination of the elements. The chemical composition of these single crystals was determined by comparing their lattice parameters with those of the standard polycrystalline samples. The IR transmission range of single crystals of (ZnSe)1-x(CuMSe2)x (M=Al, Ga, or In) is slightly narrower than that observed for pure ZnSe. However, these materials still show good transmission in the long-wavelength IR range. The addition of small amounts of CuMSe2 (M=Al, Ga, or In) considerably increases the hardness of ZnSe.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.05a
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• pp.62-65
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• 1995

CdTe crystals were grown by the vertical Bridgman method. P-type DcTe crystals were grown with Cd:Te= 1:1.001 wt. % ratio, while n-type CdTe crystals were 1:1 Also, CdTe:In crystals were investigated, Lattic constants were 6.489${\AA}$ for p-type 6.480${\AA}$for n=type and 6.483${\AA}$ for CdTe:In EPD was 10$\^$-3/-10$\^$4/cm$\^$-2/ for n-, p-type CdTd, 10$\^$4/-10$\^$5/cm$\^$-2 for Cd:Te:In using by E-Ag solution for (111) plane The carrier concentration, the resistivity and the Hall carrier mobility measured by the van der Pauw method were p=5.78${\times}$10$\^$15/cm$\^$-3/, $\rho$=20.2$\Omega$cm, ${\mu}$$\sub$p/=75.6cm$\^$-2/ V$\^$-1/ sec$\^$-1/ for p-typem n=2.98${\times}$10$\^$16/cm$\^$-3/, $\rho$=0.214$\Omega$cm, ${\mu}$$\sub$p/=978.9cm$\^$-2/ V$\^$-1/ sec$\^$-1/ for n-type and n=7.45${\times}$10$\^$16/cm$\^$-3/, $\rho$=1.54 ${\times}$10$\^$3/$\Omega$cm, ${\mu}$$\sub$p/=658.4 cm$\^$-2/ V$\^$-1/ sec$\^$-1/ for CdTe:In crystals, Transmittance of p-type CdTe was 61% that of n-type was 65%, Cd:Te:In showed 60% IR transmittance.

• Proceedings of the Korea Crystallographic Association Conference
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• 2003.05a
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• pp.19-19
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• 2003

A cubic perovskite-type CaCu₃Ti₄O/sub 12/ compound has recently drawn a great attention because of an extraordinary high permittivity (～10⁴ at 1 kHz) at room temperature and its near temperature-independence over a wide temperature region, and thus numerous literature have been reported on CCTO polycrytalline ceramics and thin films. However, only a few literature have been reported on the CCTO single due to the lack of information about the CCTO primary phase field. On the basis of our recent experimental determination of the CCTO primary phase field, we could grow ACu₃Ti₄O/sub 12/(A=Ca, Sr) single crystals using both top-seeded solution growth and flux growth methods. This presentation will include three major parts. In part I, the thermal decomposition reaction of CCTO and its primary phase field in the CaO-CuO-TiO₂ ternary system will be presented. Detailed growth conditions of ACu₃Ti₄O/sub 12/(A=Ca, Sr) single crystals and characteristics of as-grown crystals will be followed in Part II. Part III will be comprised of dielectric properties of as-grown ACu₃Ti₄O/sub 12/(A=Ca, Sr) single crystals. Our experimental results will be compared with those of previous reports for discussion.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.88-89
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• 2000

The properties for self-frequency doubling (SFD) is unique phenomena for a small number of special single crystals. It is known that there are serious limitations to vary the concentration of active ions, for example high doping of active ions from 1 to 50 atomic %, in nonlinear materials. Until now, the Nd:YAl$_3$(BO$_3$)$_4$ (YAB) and Nd:(Ce,Gd)Sc$_3$(BO$_3$)$_4$ (CSB) crystals with high doping rates are well studied for the application of SFD purpose. They have much useful SFD properties, but also have big problems in crystal growth. In case of YAB crystal, it can be grown by solution melt method with very low growth rates and easy occurrence of inclusions. In case of CSB crystal, it has optically heterogeneity problems because of disarrangement of ions in huntite structure [1]. These problems make above crystals not so attractive for optical applications. Some popular nonlinear materials, such as LiNbO$_3$(LN), KTiOPO$_4$(KTP), LiB$_3$O$_{5}$ (LBO) crystals, are impossible to substitute by Rare Earth activators because of their crystallo-chemical problems of structure. When we dope active ions with the requisite concentrations for laser generation, it results in decreasing of optical quality of crystals or destroying of acentrosymmetric structure. (omitted)d)

• Korean Journal of Crystallography
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• v.3 no.1
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• pp.37-43
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• 1992

KTiOP04 is a nonlinear optical crystal which is most widely used for frequency doubling of the radiation of Nd : YAG laser. In the experiment, sin ale crystals of KTiOP04 were grown by TSSG technique using 3K2W04·P2O5 flux. Low temperature gradient furnace suitable for KTP single crystal growth was used. Seed crystal was placed at the surface of the solution for the purpose of better observation of the growing crystals and the possibility of diameter control. Solution included 66.7mol% KTiOP04 for all experiments and its saturation temperature was 1020℃. The conditions of single crystal growth were as follows: cooling rate 0.2℃/h, crystal rotation rate 50rpm, c -axis seed. Using these conditions, single crystals up to 23 ×25×25mm3 have been groan from about 100cc solution. We have also observed a change in the crystal growth habit which resulted in the formation of large (201) faces and small (100) faces. And some crystals have (101) faces.

• Korean Journal of Crystallography
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• v.3 no.2
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• pp.120-128
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• 1992

Single crysals of BaTiO3 were grown by TSSG technique at various cooling rates. Morpolo girts, defects and domain structures of the grown crystals were investigated. At the cooling rates below 0.5℃/hr, equant single crystals were obtained and the 11111 faces were dominantly developed. If the cooling rate was much faster or if the vortical temperature gradient in the so lotion was very large, the solution became unstable and the needle formed BasTil04 o crystals were precipitated. Two sets of parallel lamella domains are arranged perpendicular to each other and the irregularly shaped boundaries are fixed between them. These sets of domains show remarkable orientation contrast in x-ray topography. Heating the crystal above 127℃, the phase transition from tetragonal to cubic occurs. The phase transition front (PTF) moves in the direction of temperature gradient. Domains in the tetragonal phase are successively rearranged and regular strain patterns appear in the cubic phase. The habit plane of PTF in BaTi03 is found to deviate from a l1101 lattice plane by app roximately 9°.

• Korean Journal of Materials Research
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• v.24 no.11
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• pp.625-631
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• 2014

To investigate the deformation properties of TiC-(5-20) mol% Mo solid solution single crystals at high temperature by compression testing, single crystals of various compositions were grown by the radio frequency floating zone technique and were deformed by compression at temperature from 1250K to 2270K at strain rates from $5.1{\times}10^{-5}$ to $5.9{\times}10^{-3}/s$. The plastic flow property of solid solution single crystals was found to be clearly different among a three-temperature range (low, intermediate and high temperature ranges) whose boundaries were dependent on the strain rate. From the observed property, we conclude that the deformation in the low temperature range is controlled by the Peierls mechanism, in the intermediate temperature range by the dynamic strain aging and in the high temperature range by the solute atmosphere dragging mechanism. The work softening tends to become less evident with an increasing experimental temperature and with a decreasing strain rate. The temperature and strain rate dependence of the critical resolved shear stress is the strongest in the high temperature range. The curves are divided into three parts with different slopes by a transition temperature. The critical resolved shear stress (${\tau}_{0.2}$) at the high temperature range showed that Mo content dependence of ${\tau}_{0.2}$ with temperature and the dependence is very marked at lower temperature. In the higher temperature range, ${\tau}_{0.2}$ increases monotonously with an increasing Mo content.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.1
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• pp.12-17
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• 1993

Growth runs of KTP single crystals were carried out by the hydrothermal method. KTP powders used for the crystal growth were prepared as a single phase by the solid state reaction of a stoichiometric mixture of $KH_2PO_4 and TiO_2$ at TEX>$800^{\circ}C$ and subsequently by the hydrothermal treatment at $250^{\circ}C$ 4m KF solution. The most effective solvents for the crystal growth of KTP were KF and K $K_2HPO_4$ solutions. Solubilities of KTP in these solutions were positive over the range $350~450^{\circ}C$.Seed crystals of good quality could be obtained by the horizontal temperature gradient method at temperatures over the range 380~430^{\circ}C$ in these solutions. The hydrothermal conditions for the high growth rates of seed crystals are as follows: growth method; vertical temperature gradient method, solvent; 4m KF or $K_2HPO_4$ solution, temperature region; $400~450^{\circ}C$, pressure region; $1000~1500kg/cm^2$, where solubility of KTP was large enough to proceed the growth. Under such conditions, seed crystals of KTP are grown at a rate of approximately 0.06-0.08mm/day in the direction of the c-axis. Morphologies of grown crystals tended to be bounded by (100), (011) and (201) faces.