• Korean Journal of Crystallography
• /
• v.12 no.1
• /
• pp.5-9
• /
• 2001

Nd/sub 0.05/Y/sub 0.95/Ca₄O(BO₃)₃(Nd:YCOB) single crystals were grown by the Czochralski method using a iridium crucible under N₂ atmosphere. Optimum growth parameters to get high quality of single crystals were 1.5∼2 mm/hr of growth rate and 10∼20 rpm of rotation rate. The grown crystals were transparent with light purple color and well-developed in cleavage planes. The crystal structure of Nd;YCOB were identified to monoclinic by XRD method. Crystal defects acting as light scattering centers, such as micro-pores, secondary phases, inclusions and cracks were not observed under the He-Ne laser illuminations. Three red, green, blue laser devices for the RGB laser oscillations were designed and then fabricated from the grown Nd:YCOB crystals according to the phase-matching angles of negative type-I which were φ=16.40°, 33.95° and θ=22.59° with the flatness of λ/6 at least, respectively.

• Korean Journal of Crystallography
• /
• v.10 no.1
• /
• pp.71-75
• /
• 1999

융액인상법에 의하여 Nd3+ 이온이 15 at% 주입된 LaSc3(BO3)4 단결정을 성장하였다. 최적의 결정성장 조건하에서 성장된 결정은 결정형이 잘 발달되고 보라색 투명하였다. 편광 현미경에 의한 결정결함 분석결과 성장된 결정 중심부에서 0.1 mm 크기의 기포가 검출되었고, B2O3가 증발하여 결정에 증착된 shoulder 부위에서는 균열이 발생되었으나 body에서는 결함이 검출되지 않았다. X선 회절에 의하여 cell parameter를 측정한 결과 a=7.73 , b=9.85 , c=12.05 , β=105.48o 및 공간군 C2/c의 monoclinic 구조로 분석되었다. 양질의 단결정을 성장하기 위한 결정성장 요소는 회전속도 10 rmp, 인상속도 1.5 mm/h이었다. 성장된 결정은 808 nm에서 강하고 넓은 흡수대와 1050∼1080 nm에 걸친 형광 방출대가 관찰되었다. 성장된 결정을 이용하여 직경 3 mm, 두께 1mm 크기의 micro-chip laser 소자의 제조기술을 확립하였다.

• Korean Journal of Crystallography
• /
• v.10 no.1
• /
• pp.76-82
• /
• 1999

융액인상법에 의하여 Garnet 구조내 결정학적 8면체 및 4면체의 양이온 자리에 전하 보상이온 Mg2+, 구조 수식이온 Sc3+ 및 laser 활성이온 Cr4+을 다양한 농도로 주입한 융액으로부터 Cr4+:YAG 단결정을 성장하고, 주입된 불순이온이 흡수계수에 미치는 영향을 규명하였다. 양질의 단결정을 성장하기 위한 인상속도와 회전속도는 각각 1.5 mm/h와 10 rmp이었으며, Cr4+:YAG 단결정은 <111> 방위로 성장하였다. 성장된 결정의 결정구조 동정 및 결정격자 상수를 측정하고, 1.064 ㎛에서의 결정화분율에 따른 흡수계수, 형광방출 스펙트럼, 유효편석계수(keff)를 보고하였다.

• Korean Journal of Crystallography
• /
• v.11 no.1
• /
• pp.34-41
• /
• 2000

The group-theoretical approach analyzing the domain structure and the domain wall orientations of the ferroelastic crystal was introduced. These theoretical results were investigated by comparing them with the experimental results of several ferroelastic crystals, CsPbCl₃, Pb₃(PO₄)₂, and LiCsSO₄, which were grown by the Czochralski and solution methods, respectively. both results were agreed well and also consistent with those of previous works such s the strain method and the geometrical consideration. The group-theoretical approach showed that the ferroelastic domain walls must be the crystallographical prominent planes with fixed indices and classified by the symmetry elements characterizing the permissible domain walls. So the group-theoretical approach could be suggested as a new method for analyzing the structure of the ferroelastic domain and domain walls.

• Proceedings of the Korea Association of Crystal Growth Conference
• /
• 1996.06a
• /
• pp.351-374
• /
• 1996

Various types of garnet compounds were synthsized by iso-and aliovalent substitutions and sintering method. Among them, fiber shapes of garnet crystals were grown from the $Ca_3Li_xNb_{(1.5+x)}Ga_{(3.5-2x)}O_{12}$ melt where x = 0 ~ 0.5 by modified micro-pulling down method in air using Pt crucibles. The measured lattice constants as a function of solidification fraction of grown fiber crystals are about $12.54\;{\AA}$ irrespective of x. It was found that the $Ca_3Li_{0.275}Nb_{1.775}Ga_{2.95}O_{12}$ garnet melts congruently at about $1450\;^{\circ}C$ based on the purities of garnet phase and variations of lattice parameter. Transparent and bubble-free crystals of x = 0.25 and 0.275 were grown by Czochralski techniques in air using Pt crucibles. An absorption spectrum is also reported.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.5 no.4
• /
• pp.408-413
• /
• 1995

We investigated the effect of mechanical backside damage upon minority carrier recombination lifetime measurement in Czochralski silicon substrate by laser excitation/microwave reflection photoconductance decay method. The intensity of mechanical damage was evaluated by X-ray double crystal rocking curve, X-ray section topography and wet oxidation/preferential etch methods. The data indicate that the higher the mechanical damage intensity, the lower the minority carrier lifetime, and the threshold full width at half maximum value which affect minority carrier lifetime measurement is about 13 secs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07b
• /
• pp.965-967
• /
• 2003

Czochralski pulling method에 의해 성장된 고농도 도핑 Nd:LSB의 광학적 특성을 조사하였다. 결정 성장조건에 의해 달라지는 space group은 지금까지 C2/c, R32, Cc와 C2등 4가지가 보고되었으며, 기본적으로 6방정계의 구조를 가지고 비선형 광학 결정으로서의 특성을 보였다. x선 회절 분석계를 이용하여 구조를 분석하였고, 도핑 농도에 따른 형광 수명의 변화, 분산곡선 특성을 조사하였다. 또한 흡수 및 저온 형광 스펙트럼을 이용하여 도핑 농도 및 space group의 변화에 따른 에너지 준위의 변화를 관찰하고 비교하였다.

• Journal of Mechanical Science and Technology
• /
• v.15 no.12
• /
• pp.1876-1881
• /
• 2001

We present the numerical analysis of the growth of a silicon (Si) single crystal. In the MCZ (Magnetic-field-applied Czochralski) method, two magnetic fields that stand opposite to each other generate a cusp magnetic field. In this work, the three cusp magnetic fields used for the analysis are an extern magnetic field, a surface magnetic field and an internal magnetic field. Each case was evaluated mainly as to the degree of stirring, shaft symmetry and the stability of the flow. As a result, the cusp magnetic field that yielded to best conditions was the internal magneic field.

• Journal of the Korean Ceramic Society
• /
• v.27 no.4
• /
• pp.567-573
• /
• 1990

Solidification condition for preparing transparent ${\gamma}$-6Bi2O3.GeO2 polycrystals by unidirectional solidification of melt, were investigaetd and the properties of the polycrystals prepared were measured. The ${\gamma}$-6Bi2O3.GeO2 polycrystals showing transparency like a single crystal were obtained by the unidirectional solidification of ${\gamma}$-6Bi2O3.GeO2 melt at a solidification rate of 0.5mm/h under a thermal gradient of 12$0^{\circ}C$/cm. The transparent polycrystals obtained showed the same photoconduction and optical activity as the ${\gamma}$-6Bi2O3.GeO2 single crystals grown by Czochralski method. But the electro-optic effect of polycrystals was heterogeneous because the colummar ${\gamma}$-6Bi2O3.GeO2 crystals were not oriented to the particular crystallographic direction.

• Journal of the Korean Ceramic Society
• /
• v.36 no.12
• /
• pp.1364-1368
• /
• 1999

Langasite( La3Ga5SiO14) is suitable for new piezoelectric properties. Langasite can be applied for communication de-vices due to intermediate piezoelectric properties which are similar to those of quartz and LiTaO3 in its acoustic cha-racteristics. In this study Langasite( La3Ga5SiO14) single crystals were successfully grown by using self-designed Czo-chralski system. From the results of optical properties it was found that crystals having a high quality and higher optical transmittance were grown at atmosphere of 1 to 30 vol% of oxygen content.