• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.108-108
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• 1998

최근의 GaN에 관한 연구는 주로 MOCVD법과 MBE법이 이용되고 있으며 대부분 800¬1$\alpha$)()t 정도의 고옹에서 이루어지고 었다. 그러나 이러한 고온 성장은 GaN 성장 과청에서 질 소 vacancy를 생성시켜 광특성을 저하시키고 청색 발광충인 InGaN 화합물에 In의 유입울 어 렵게 하며 저온에서보다 탄소 오염이 증가하는 동의 문제캠을 가지고 있다. 이러한 고온 생장 의 문제점을 해결하기 위한 방법중의 한 가지로 제시되고 있는 것이 저온 성장법이다. 본 연구 에 사용된 RPE-UHVCVD법은 Nz률 rf plasma로 $\sigma$acking하여 공급함으로써 NI-h롤 질소원으 로 사용하는 고온 성장의 청우와는 다르게 온도에 크게 의존하지 고 질소원올 공급할 수 있 어 저옹 성장이 가능하였다. 기판으로는 a - Alz03($\alpha$)()1)를 사용하였고 3족원은 TEGa(triethylgallium)이며,5족원으로는 6 6-nine Nz gas를 rf plasma로 cracking하여 활성 질소원올 공급하였다 .. Nz plasma로 질화처리 를 한 sapphire 표면 위에 G따애 핵생성충을 성장 옹도(350 t, 375 t, 400 t)와 성장시간(30 분,50 분) 그리고 VIllI비(1$\alpha$)(), 2뼈)둥을 변화시키면서 성장시킨 후 GaN 에피택시충을 450 $^{\circ}C$에서 120 분 동안 성장시켰다 .. XPS(x-ray photoelectron spectroscopy), XRD(x-ray d diffraction), AFM(atomic force microscope)둥올 이용하여 표면의 조성 및 morphology 변화와 결정성을 관찰하였다. X XPS 분석 결과 질화처리를 한 sapphire 표면에는 AlN가 형성되었다는 것을 확인 할 수 있 었으며 질화처리를 한 후 G따J 핵생성충올 성장시킨 경우에 morphology 변화를 AFM으로 살 펴본 결과 표면에 facet shape의 island가 형성되었고 이러한 결파는 질화처리 과청이 facet s shape의 island 형성을 촉진시킨다는 것을 알 수 있었다. 핵생성충의 성장온도가 중가함에 따 라 island의 모양은 round shape에서 facet shape으로 변화하였다. 이러한 표면의 morphology 변화와 GaN 에피택시충의 결정성과의 관계를 살펴보면 GaN 에피택시충 표면의 rms(root m mean square) roughness가 중가하는 경 우 XRD (j -rocking curve의 FWHM(full width half m maximum) 값이 감소하는 것으로 나타났다. 이러한 현상은 결정성의 향상이 columnar 성장과 관계가 었다는 것올 알 수 있었다 .. columnar 성장은 결함의 밀도가 낮은 column의 형생과 G GaN 에피택시충의 웅력 제거로 인해 G값{의 결정성을 향상시킬 수 있는 것으로 생각된다. 톡 히 고온 성장의 경우와는 달리 rms roughness의 중가가 100-150 A청도로 명탄한 표면올 유 지하면서 결정성을 향상시킬 수 있었다. 본 실험에서는 핵생성충올 375 t에서 30 분 생장시킨 경우에 hexagonal 모양의 island로 columnar 성장을 하였고 GaN 에피태시충의 결정성도 가장 향상되었다 이상의 결과로부터 RPE-UHVCVD법용 이용한 GaN 저온 성장에서도 GaN의 결청성올 향 상시킬 수 있음융 확인할 수 있었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.6-13
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• 1999

NaX zeolite crystal were grown from seed elements of synthetic NaX(2~3$\mu\textrm{m}$) Powder in a mother liquor having an approximate reactant composition ${4.12{Na}_{2}O{\cdot}{Al}_{2}{O}_{3}{\cdot}3.5{SiO}_{2}{\cdot}593{H}_{2}O$.The result was that crystallization time of NaX zeolite was reduced with adding seed materials to the initial mixture and crystal size was reduced . but with increasing crystallization time, NaX zeolite. In this study, We investigated detailed factors which NaX crystal has been determined by a combination of SEM, XRD, FT-IR, and BET.

• Applied Chemistry for Engineering
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• v.4 no.1
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• pp.94-102
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• 1993

The effects of temperature and of $Na_2O$ and $SiO_2$ contents on the crystallization of zeolite A were studied, by examining crystallization curves and particle size distributions of final products at various crystallization conditions. Crystallization process could be simulated adopting the assumptions of constant linear growth rate and equilibrium between amorphous solid phase and soluble species. Rate constants were determined by comparing the simulated crystallization curves with experimental data. Rate constant for linear growth increased with temperature and crystallization rate at different mole ratio of $Na_2O/H_2O$ correlated reasonably well with increase of soluble species. The rate constant of crystallization did not increase with increase in mole ratio of $Na_2O/H_2O$, but the rate of nuclei formation and the fraction of soluble species were enhanced. The rate constants for linear growth of zeolite A were determined as $0.07{\sim}0.24{\mu}m{\cdot}min^{-1}$ at these experimental conditions Apparent activation energy was estimated as $49kJ{\cdot}mol^{-1}$.

• Korean Journal of Crystallography
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• v.7 no.2
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• pp.183-190
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• 1996

Single crystals of ZnO were grown hydrothermally with KOH solution in silver lined autoclave. The effect of LiOH and NH4OH on the morphology of as-grown crystals was studied. As-grown crystals were pale green and the maximum size was 30×30×20mm3. Addition of LiOH reduced the density of flaws on the (0001) face of as-grown ZnO crystals. In highly concentrated KOH solution, ZnO had a strong tendency to grow along the c-axis. When 1.0-2.0 M of NH4OH was added into mineralizer, growth rate along the direction of a-axis increased. From this result, ZnO single crystals of equant-faced hexagonal prism could be grown with acicular seeds.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.1
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• pp.76-82
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• 1994

Single crystals of Potassium Titanyl Phosphate (KTP) were grown from the flux of $K_6P_4O_13(K_6)$ using a high temperatures solution growth method. To grow the large KTP crystal without inclusion, the temperature gradient in furnace, crystal rotation, orientation of seed crystal, and the cooling rate were controled. The KTP crystals are up to $10(a){\times}28(b){\times}33(c)mm^3$ in size. We investigated the optical inhomogeneity in this KTP crystal by the SHG power measurement and TEM analysis.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.4
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• pp.539-543
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• 1998

The relationship of growth-in defects such as crystal originated particles (COP), flow pattern defects(FPD), laser scattering tomography defects (LSTD) was investigated in Cz-Si single crystals which had different pulling speed during crystal growing. It is concluded that the density and radial distribution of grown-in defects is strongly dependent on the pulling speed. And as the generation areas of these grown-in defects in a wafer are identical in radial position, they can be generated from same origin during crystal growing.

• Journal of the Korean Vacuum Society
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• v.5 no.4
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• pp.387-390
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• 1996

The study has been performed that the high purity of platinum crystal was grown by rf floating zone refined technique. Direct electric current was also present to examine the controlling striated structure during the sample grown. It has been proved that current and orientation could affect suppression of the striation structure in Pt. Substructure in Pt was thermally unstable and was able to be removed by the annealing technique.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.4
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• pp.378-385
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• 1995

The growth processes of improved methods for MBE, LPE and $\mu$ - PD methods are discussed taking the oxide materials, especially those of Bi - Sr - Ca - Cu family $LiNbO_3$ and $K_3Li_2Nb_5O_{15}$ family as examples. It is suggested that the crystal growth far from equilibr iu m including composition homogeneity has been achieved to satisfy in understanding and controlling the atomic interfaces.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.3
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• pp.293-300
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• 1996

A continuous growth method (Orr's method) were developed to grow LiNbO3 single crystals. The optimum growth condition established are as follows; When the controlled temperature of a platinum crucible were 1190℃∼1210℃, the pulling rate was 2 mm/hr, the feeding rate was 1.5∼2.5 g/hr, and the rotation speed was 20 rpm. The phase and growth orientation of the grown LiNbO3 crystals wer characterized by a X-ray diffraction method. The overflowing phenomena, which induced cracking into the grown crystal during the process, was effectively suppressed by the control of the growth parameter.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.6
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• pp.373-377
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• 2000

For 6H-SiC single crystals which was obtained by sublimation growth (modified Lely process), the relation between the defects and the etch pits to be formed at the site of dislocations were discussed. Typical hexagonal etch pits were formed on (0001) basal plane. The similar hexagonal etch pit shapes were formed on the site of micropipe defects and it was realized that internal planar defects was formed with the same matrix crystal structure as grown crystals, through the observation of the etching morphology at those internal defects.