• Journal of the Korean Ceramic Society
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• v.24 no.5
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• pp.461-469
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• 1987

Single crystals of Mn-Zn Ferrite were grown by slow cooling method using Na2B4O7 as flux agent. The effects of flux content and cooling rate on the types of crystals, and the relation between supersaturation and growth mechanism were studied. As a result, the types of grown crystals occurred as plate, hopper and octahedral crystals. The occurrence of these crystal types was dependent on flux content. The habit was found to correlate with the growth rate and supersaturation. The lateral growth of a dendritic crystal is related to the twin layer. The growth of crystals from borax melts mainly occurred by the layer-spreading growth following corner and edge nucleation caused by high supersaturation in the melt. Especially, the plate crystals were produced on top of the melts. The hopper and octahedral crystals occurred at lower supersaturation than the plate crystals.

• Journal of the Korean Institute of Navigation
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• v.19 no.4
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• pp.83-92
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• 1995

In this study, a vertical type LPE system has been developed for III-V semiconductor compounds single crystal growth. On the basis of the experience & basic study using this system, the system modification has been carried out for a ultra thin multi-layer single crystal. The temperature fluctuation was within ${\pm}0.006^{\circ}C$ at $800^{\circ}C$, temperature uniformity for graphite boat around was within ${\pm}0.15^{\circ}C$ at $650^{\circ}C$, and cooling rate was controllable from $2.2^{\circ}C$/min to $0.05^{\circ}C$/min. As a result it is considered to satisfy the condition to grow a ultra thin layer single crystal of III-V semiconductor compounds.

• Proceedings of the Optical Society of Korea Conference
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• 2001.08a
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• pp.246-247
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• 2001

Undoped YCa$_4$O(BO$_3$)$_3$ (sp. gr. Cm) single crystals as well as singly or co-doped with Yb, Er and Ce were grown using Czochralski technique. With the aid of x-ray analysis, crystallographic data of Ce, Er, Yb:YCA$_4$O(BO$_3$) crystals were found.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.383-387
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• 1998

The vacuum-Bridgman equipment for large size diameter (4 inch more over) crystal growth was organized simply and the $CaF_2$ single crystal which was grown in the conditions of growth rate of 2mm/hr, freezing temperature gradient of $12^{\circ}C$/cm, have analyzed to keep excellent properties. Using Mo thermal reflector of umbrella shape, it could be eliminated the formation of polycrystalline. The preferential growth direction was (111) and the calculated lattice parameter was $5.460 \AA$ by XRD peaks. The secondary phases, also, was not formed by means of powder-XRD analysis. The value of EPD is $1.4{\times}10^4 \textrm{cm}^{-2}$ and the optical quality, which is the transmittance is 91% up in UV region, is suitable for optical components of UV applications.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.4
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• pp.550-554
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• 1998

We suggested the new method of thermal screen in Bridgman-Stockbarger method to control the polygrain, the internal cavities and solid-liquid (SL) interface. $CaF_2$ single crystal of 6 inch was grown perfectly when we adopted to use a graphite pipe and a ceramic warmer in the conditions of growth rate 2 mm/hr, vertical temperature of $14^{\circ}C$ for freezing and temperature of $1324^{\circ}C$ at conical tip of crucible. The light scattering phenomena occurred by internal cavities were controlled as decreasing the freezing rate to 2 mm/hr and/or as adopting the rotation of melt (7 rpm).

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.4 no.1
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• pp.121-131
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• 2000

Melt flow, heat and mass transfer of oxygen have been analyzed numerically in the process of Czochralski single crystal growth of silicon under the influence of misaligned cusp magnetic fields. Since the silicon melt in a crucible for crystal growth is of high temperature and of highly electrical-conducting, experimentation method has difficulty in analyzing the behavior of the melt flow. A set of simultaneous nonlinear equations including Navier-Stokes and Maxwell equations has been used for the modelling of the melt flow which can be regarded as a liquid metal. Together with the melt flow which forms the Marangoni convection, a flow circulation is observed near the comer close both to the crucible wall and the free surface. The melt flow tends to follow the magnetic lines instead of traversing the lines. These flow characteristics helps the flow circulation exist. Mass transfer characteristics influenced by the melt flow has been analyzed and the oxygen absorption rate to the crystal has been calculated and turned out to be rather uniform than in the case of an aligned magnetic field.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.2
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• pp.197-202
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• 2023

Calcium fluoride (CaF₂) single crystal is applied to numerous industrial applications, especially for optical uses. To have excellent optical transmission properties, however, CaF₂ crystals should be carefully fabricated through liquid-phase crystal growth techniques. In this study, as one of the early stage research activities to grow CaF₂ crystals with a good transmittance at the ultraviolet wavelength range, computational thermodynamic models were provided to deepen the understanding of the crystal growing processes of CaF₂ under various conditions. To remove point defects and oxygen impurities in the grown CaF₂ crystals, the system was thermodynamically evaluated to get optimal process conditions. From the reviews of previous experimental studies, computational thermodynamic approaches were found to be an effective and powerful tool to understand the meaning of the crystal growth processes and to obtain optimal process conditions.

• Korean Journal of Crystallography
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• v.8 no.1
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• pp.38-47
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• 1997

A new weighing sensor for the automatic diameter control system of the crystal growth is developed in this study. This weighing sensor measures the frequency of the vibrating element which is lineally changing with respect to weight. The signal and the power of this system are transmitted without any physical contact, so that this sensor offers high accuracy and resolution. This system consists of a string, a sinusoidal wave generator, an automatic amplification adjusting circuit, signal transformers and a PCB. 4 kinds of programs are developed for checking DAC, weight calibration and controlling growth process. The measurements of the standard deviation and the resolution show $\pm0.10g$(measured at every second) and $5{\times}10^{-5}$, respectively, This weighing sensor is effective under high pres-sure of 200 atm, high temperature and vacuum condition. The weighing system can control the temperature in the accuracy of $\pm0.025^{\circ}C$ with the 'signal divider'. The optical quality single crystals of $(YGd)_3Sc_2Ga_3O_{12},\;Er-Y_3Sc_2Al_3O_{12},\;and\;Bi_{12}GeO_{20}$ have been grown by Czo-chralski method using this auto-diameter control system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.197-198
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• 2008

이 논문에서는 다양한 SiNx의 band gap을 이용하여 MIS 구조의 메모리 소자를 제작하고 이를 분석하였다. SiNx 박막은 증착 가스비에 따라 다양한 band gap을 가지게 된다. 본 실험에서는 $SiH_4$ 가스와 $NH_3$ 가스를 사용하여 SiNx 박막을 증착하였다. n-type 단결정 실리콘 기판위에 다양한 가스비에 따라 단일 SiNx 박막을 증착 및 분석하였고, 이를 이용하여 NNN 구조의 MIS 소자를 제작하였다. 제작된 소자는 4.6 V의 hysteresis roof 폭과 1000 초 후에 84.8 %의 retention 값을 갖는 우수한 메모리 특성을 보였다.

• Korean Journal of Crystallography
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• v.2 no.1
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• pp.1-11
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• 1991

When GaAs single crystals are grown by LEC method, a serious problem is that longitudinal twins are often generated. the growth axis is changed from (100) to (221) direction by logitudinal twin. In this experiment, 3 inch GaAs single crystals, slaving (100) uonh axis, were von by LEC method. Striations and edge facets generated during crystal growth, were observed by SPW photo-etching. Relationship between striations and edge facets was studied. Instability of their generation was the cause of goneration of longitudinal twins. The shape of striations was changed with the growth conditions such as crystal diameter and melt volume. In the region of crystal edge: there was the microscopic fluctuation by the instability of melt convection. Edge facets consisting of {111} plane developed well in the region which striation were convex to the melt. Because the angle between striation and {111} edge facet decreased in that region. Longitudinal twins were generated on the crystal surface at the <111> direction which is perpendicular to the growth axis. These were generated by unstable melt convection and propagated in the crystal as crystal grew. Longitudinal twins were generated when regrowth rate was very fast after {111} edge facets were remelted. So, in order to supress the generation of longitudinal twin, abrupt change of melt convection must be prohibited.