• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.939-942
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• 2002

The optically addressed and electrically addressed spatial phase only light modulators without pixelized structures have been developed. A sufficient phase modulation capability and a high diffraction efficiency of these devices are useful for practical applications.

• 한국수소및신에너지학회논문집
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• 제22권3호
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• pp.349-356
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• 2011

During the process of synthesis of $TiO_2$ powders using a high-speed planetary milling machine, Fe metallic powders were created which could be dissolved in sulfuric acid solution. With adding $NH_4OH$ solution to the $TiO_2$ powder, it was found that the crystal structure of the synthesized powder did not change and the crystal size decreased slightly. However, when the sulfur powder is mixed with $TiO_2$, the crystal structure of the MA powder was changed from anatase into rutile phase and its size decreased significantly which is in the order of nm in diameter. In case of mechanical alloying with $TiO_2$ powder only, the crystal structure of the powder was transformed into rutile phase and its size was greatly reduced into several nm. Because its size becomes fine, the energy band gap of its rutile phase is larger than that of bulk states (3.0eV).

• 열처리공학회지
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• 제31권5호
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• pp.237-243
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• 2018

In-rich InGaN epilayers were grown on (0001) sapphire substrates by radio-frequency plasma-assisted molecular beam epitaxy (RF-MBE). InGaN epilayers grown at various growth condition were observed by SEM, XRD, and RHEED. When plasma power of nitrogen increased from 290 to 350 W, surface morphology and crystal quality became worse according to more active nitrogen on the surface of InGaN at N-rich growth condition. As In composition was reduced from 89 to 71% by changing the incoming flux of In and Ga, surface morphology and crystal quality became worse. In addition, weak peaks of cubic InGaN phase was observed from InGaN layer with 71% In composition by XRD ${\Phi}$ scan measurement. When growth temperature decreased from 500 to $400^{\circ}C$, RHEED diffraction pattern was changed to be from streaky to spotty which means atomically rough surface, and spotty pattern showed cubic symmetry of InGaN clearly. XRD ${\Phi}$ scan measurement gave clear evidence that more cubic InGaN phase was formed at low growth temperature. All these results indicates that extremely low surface mobility of Ga adatom caused inferior crystal quality and cubic InGaN phase.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1996년도 The 9th KACG Technical Annual Meeting and the 3rd Korea-Japan EMGS (Electronic Materials Growth Symposium)
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• pp.528-528
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• 1996

• 대한화장품학회지
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• 제48권1호
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• pp.55-64
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• 2022

Cleansing foam이라 불리는 지방산 칼륨 cream soap은 crystal gel 구조로 이루어져 있어 유화계와는 달리 전단응력에 약하며 고온의 보관조건에서 쉽게 분리되는 특성을 보여준다. Crystal gel 구조는 지방산의 종류 및 비율, 중화도, polyol의 종류와 사용량에 따라 크게 영향을 받는다. Crystal gel 구조에 미치는 이들의 영향을 조사하기 위해 water/potassium hydroxide (KOH)/fatty acid ternary system에서 실험을 실시하였다. Differential scanning calorimeter (DSC) 측정 결과 myristic acid (MA) : stearic acid (SA) = 3 : 1 비율에서 공융점(eutectic point)를 갖고 이 혼합비가 가장 안전한 삼성분계(ternary system)를 만든다는 것을 발견했다. 점도 측정과 편광현미경 (POM) 관찰 결과 중화도는 75% 부근이 최적이라고 판단된다. 삼성분계의 melting point (T_m)이 보관온도보다 높을 때, 그리고 crystal phase가 lamellar gel phase로 상 전이가 일어날 때 안정하나 지방산 함량의 증가는 안정성에 거의 영향을 미치지 않는다. 삼성분계에 polyol의 첨가는 T_m을 변화시키고 상전이를 일으키는데 중요한 역할을 한다. 클렌징폼의 구조는 저온 주사전자현미경 (Cryo-SEM), 소각 및 광각 X-선 산란 (SAXS, WAXS) 분석으로 규명하였다. Butylene glycol (BG), propylene glycol (PG), dipropylene glycol (DPG)은 T_m을 낮추어주며 lamellar gel phase 형성을 어렵게 하는 반면 glycerin, PEG-400, sorbitol은 T_m을 상승시키고 lamellar gel phase 형성을 용이하게 하며 안정한 삼성분계를 만든다.

• 한국자기공명학회논문지
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• 제21권2호
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• pp.63-66
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• 2017

The $^{14}N$ NMR spectra for $(NH_4)_2SO_4$ crystals were obtained near the phase transition temperature $T_C=223K$, and were found to precisely reflect the symmetry change in the crystal at this first-order phase transition. Changes in the resonance frequencies near $T_C$ were attributed to the structural phase transition. In the ferroelectric and paraelectric phases, two inequivalent NH4 groups were distinguished in the $^{14}N$ NMR spectra. The two types, $NH_4$(1) and $NH_4$(2), have slightly different local environments. Consequently, we conclude that the phase transition is caused by the change in the environment of the $^{14}N$ nuclei in the $NH_4$ groups, rather than by the $SO_4$ groups.

• 한국결정성장학회지
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• 제14권5호
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• pp.193-198
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• 2004

$(TbBi)_3(FeAIGa)_5O_{12}(TbIG)$, $(EuBi)_3(FeAIGa)_5O_{12}(EuIG)$, $(EuTbBi)_3(FeAIGa)_5O_{12}(EuTbIG)$ 가네트 막을 $PbO-B_2O_3-Bi_2O_3$ 융제를 사용하여 $(GdCa)_3(GaMgZr)_5O_{12}(SGGG)$ 기판 위에 liquid phase epitaxy(LPE) 방법으로 성장시켰다. 성장된 TbIG, EuIG, EuTbIG 가네트 막의 포화자계값은 각각 150 Oe, 950 Oe, 170 Oe를 보였으며, magnetic force microscope(MFM) 분석을 측정 한 결과 TbIG 막에서는 단일 자구가 관찰되었으며, EuIG와 EuTbIG 막에서는 다 자구가 관찰되었다.

• 한국결정성장학회지
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• 제34권1호
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• pp.36-39
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• 2024

최근 전력반도체에 대한 관심이 확대되고 있는 가운데, SiC와 GaN 등의 광에너지갭 소재에 의한 소자화 및 응용에 대한 연구가 수행되고 있다. AlN 단결정은 이들 보다 더 큰 에너지갭을 갖기 때문에 대전력 소자화에 대한 연구도 진행중에 있으나, 상용화된 웨이퍼는 아직 보고되고 있지 않아 이에 대한 연구가 필요하다. 본 연구에서는 AlN 단결정을 제조하기 위하여 HVPE(Hydride vapor phase epitaxy) 법을 적용하였고, 자체 제작 설비를 이용하여, 벌크 단결정을 얻어내고자 하였으며, 이를 위해 단결정의 성장 조건을 확보하고자 한 결과를 보고하고자 하며, 온도의 변화에 따라 성장된 결정의 형상의 변화에 대하여 보고하고자 한다.

• 한국결정성장학회지
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• 제8권2호
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• pp.324-331
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• 1998

2, 5, 10 mol% YAG(yttrium aluminum garnet) 분말을 액상 소결조제로 $\alpha$상 탄화규소 분말에 첨가한 후 $1850^{\circ}C$에서 소결시간을 달리하여 소결체를 제조한 다음, 소결시 일어나는 미세구조 변화를 첨가된 액상량과 소결시간의 변화에 대하여 고찰하였다. 각 조성중 2시간 소결한 시편에서 가장 높은 밀도를 나타냈으며, 소결시간이 길수록 액상의 기화로 인하여 중량감소량이 점차 증가하였다. 또한 첨가된 YAG 액상량이 증가할 수록 상대밀도(apparent density)와 중량감소량은 증가하였으나 입성장속도는 감소하였다. 액상량이 적은 시편에서는 소결시간이 길수록 일부 6H상의 탄화규소 입자가 4H상 탄화규소 입자로 상전이 되었으며, 이로 인하여 막대상 입자들이 일부 존재하였다.

• 한국세라믹학회지
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• 제33권1호
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• pp.56-64
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• 1996

A large amount of papers about the cubic-to-tetragonal phase transition the ferroelectric domain structures of the BaTiO3 were already reported but there exist still some needs to observe the domain behaviors directly. In this study the domain structures of the tinned plates prepared from ta single crystal grown by the TSSG technique were observed using a polarizing microscope TE and X-ray topography. The spatial relation be-tween the orientation states of domains was investigated and the effects of external stresses and electric fields on the behaviors of ferroelectric and ferroelastic domains were studied. All the 90$^{\circ}$walls cut off in the crystal are the wedge shaped lamellar domains and all the straight boundaries in the observed domain patte군 can be interpreted as the head-to-tail 90$^{\circ}$walls. The irregular overlapped boundaries commonly observed by using a polarizing microscope and X-ray topography are complex combinations of well-known 90$^{\circ}$walls and are domain walls were predominant and were stabilized after surface polishing. In the paraelectric phase region the domain walls vanished but the residual surface strain patterns could be seen at the same positions of the stabilized 90$^{\circ}$a-a walls in the tetragonal phase region, These stabilized walls resulted from the surface strain had a memory effect in domain formation during the repeated phase transitions and could notr be affected by an external electtric field.