• 한국결정성장학회지
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• 제8권2호
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• pp.278-285
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• 1998

$(A_{1-x}A^'_x)_2ZnCl_4$혼정에서 C-IC 상전이가 A' ions의 pinning 효과에 의해 x의 증가에 따라 사라지는 것은 알려져 왔다. 본 연구에서 우리는 C상에서 polarization 방향이 파괴되지 않고 IC상에서 long range ordering을 유지하는 새로운 혼정인 $K_2Zn_{1-X}Co_XCl_4$결정을 소개한다. 우리는 Czochralski법으로 여러비율에 대한 (x=0, 0.001, 0.005, 0.01, 0.1, 0.3, 0.5, 0.7, 1) $K_2Zn_{1-X}Co_XCl_4$혼정을 육성하였으며 육성된 결정의 성분분석, 열적분석 및 x에 따른 C-IC 상전이의 존재를 확인하였다.

• 한국결정성장학회지
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• 제8권1호
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• pp.187-192
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• 1998

일반적으로 재료의 응고조직은 주상정과 등축정 수지상 영역으로 이루어지는데 이것은 제품의 기계적, 물리적 성질과 밀접한 관계를 가지기 때문에 주상정-등축정 천이에 관한 많은 이론적 연구가 행하여지고 있다. 본 연구에서는 J.D. Hunt에 의하여 일방향응고시 주상정앞에서의 핵생성과 결정성장조건을 이용하여 구하여진 해석학적 주상정-등축정 조건식을 바탕으로 응고속도에 따라 변하는 분배계수와 액상선기울기를 적용하여 수정된 조건식을 구하였다. 그리고 Al-Cu합금에 대하여 응고변수인 핵생성수, 핵생성온도, 합금의 조성, 응고속도 온도기울기에 따른 천이현상의 변화를 조사하였다.

• Journal of the Optical Society of Korea
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• 제20권6호
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• pp.733-738
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• 2016

We calculate optical properties of guided modes of a hybrid-guiding photonic crystal fiber. The design and modeling of such hybrid-guiding PCF is made by replacing air holes with inserts of high refractive index material layer by layer in order. The optical properties such as mode intensity profile, mode dispersion, optical birefringence, confinement loss, and chromatic dispersion during transition of the guiding mechanism are analyzed and discussed. The guided modes in the hybrid-guiding region are also compared with those of reference index-guiding and bandgap-guiding photonic crystal fibers.

• 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.19-37
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• 1996

Scanning electron microscopy (SEM) has been applied to observe directly the {{{{ SQRT { 19} }}}}${\times}${{{{ SQRT { 19} }}}} and (1${\times}$1)HT reconstructions and the transition associated step bunching on the GaAs (111)B surfaces under As pressure. Close to the transition point, {{{{ SQRT { 19} }}}}${\times}${{{{ SQRT { 19} }}}}an d (1${\times}$1)HT reconstructions are observed in dark and bright domains by SEM and determined by micro-probe reflection high-energy electron diffraction (${\mu}$-RHEED). The reconstruction diagram shows hyster-esis. The stepped surface morphology during the reconstruction transition was unstable. Heavy step bunching with rough macrostep edges was observed.

• Journal of Information Display
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• 제13권1호
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• pp.31-36
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• 2012

Ferroelectric liquid crystal parameters, spontaneous polarization, and transition temperature were studied as a function of cell thickness. These parameters were found to increase with increasing cell thickness, but an exception was observed for the transition temperature in the case of a thin cell. A simple Landau model is presented to interpret the theoretical and experimental observations. The anomalous behavior is attributed to the electroclinic effect and is explained using the Landau model.

• 한국세라믹학회지
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• 제36권8호
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• pp.859-862
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• 1999

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.347-351
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• 2003

A p-$CdIn_2Te_4$ single crystal has been grown by the Bridgman method without a seed crystal in a tree-stage vertical electric furnace. From photocurrent measurements, it was found that three peaks, A, B, and C, corresponded to an intrinsic transition due to the band-to-band transition from the valence band states ${\Gamma}_7(A),\;{\Gamma}_6(B),\;and\;{\Gamma}_7(C)$ to the conduction band state ${\Gamma}_6$, respectively. Also, the valence band splitting of the $CdIn_2Te_4$ crystal has been confirmed by photocurrent spectroscopy. The crystal field splitting and the spin orbit splitting were obtained to be 0.2360 and 0.1119 eV, respectively. Also, the temperature dependence of the band gap energy of the $CdIn_2Te_4$ crystal has been driven as the following equation of $E_g(T)\;=E_g(0)\;-\;(9.43\;{\times}\;10^{-3})T^2/(2676\;+\;T)$. In this equation, the Eg(0) was estimated to be 1.4750, 1.7110, and 1.8229 eV at the valence band state A, B, and C, respectively. The band gap energy of the p-$CdIn_2Te_4$ at room temperature was determined to be 1.2023 eV.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 15TH KACG TECHNICAL MEETING-PACIFIC RIM 3 SATELLITE SYMPOSIUM SESSION 4, HOTEL HYUNDAI, KYONGJU, SEPTEMBER 20-23, 1998
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• pp.97-102
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• 1998

Transition metal Cr3+ and Fe3+ ion was diffused in white sapphire {0001}, {1010} crystal plane which were grown by the Verneuil method. It enhanced and changed the physical, electrical and optical properties of sapphires. After mixing the metallic oxide and metal powder, it were used for diffusion. Metallic oxide was synthesized by precipitation method and it's composition was mainly alumina which doped with chromium or ferric oxide. In case using metallic oxide, the dopping was slowly progressed and it needed the longer duration time and higher temperature, relatively. Metallic powder was vapoured under 1x10-4 torr of vacuum pressure at 1900(iron metal) and 2050(chromium)℃, first step. Diffusion condition were kept by 6atm of N2 accelerating pressure at 2050∼2150℃. Each surface density of sapphire crystal are 0.225(c) and 0.1199atom/Å2(a). The color of the Cr-doped sapphires was changed to red. Dopping reaction was come out more deep in th plane of {1010} than {0001}. It was speculated that the planar density was one of the factors to determine diffusion effect.

• 한국수소및신에너지학회논문집
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• 제14권2호
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• pp.97-104
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• 2003

The structural transitions of the matrix and the second phases of $Ti_{1.0}Mn_{0.9}V_{1.1}$ and $Ti_{1.0}Cr_{1.5}V_{1.7}$ alloys upon hydrogenation have been investigated at 293K. The effect of hydrogen isotope on their crystal structures has been also discussed. The crystal structures, Phase abundance and lattice parameters of the hydrides were determined by the Rietveld method using X-ray diffraction data. At the experimental temperature, the $Ti_{1.0}Mn_{0.9}V_{1.1}$ alloy and $Ti_{1.0}Cr_{1.5}V_{1.7}$ alloy revealed different structural transition processes upon hydrogenation although the crystal structures of these two alloys are both BCC at room temperature. The second phases such as Ti-rich phase with $NiTi_2$ structure and $\alpha$-Ti with HCP structure absorbed hydrogen at relatively low hydrogen pressures and the phase abundance remained almost constant. This means that it is desirable to decrease the amount of the second phases as far as possible in order to increase the effective hydrogen storage capacities of the alloys. The crystal structures of corresponding isotope hydrides, the phase abundance and the lattice parameters did not depend on the kind of hydrogen isotope, but only on the hydrogen content.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.191-192
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• 2002

We reported pushing of colloidal particles by a moving isotropic-nematic phase boundary. Here, we report tailoring the structure of 3-dimensional networks formed by these particles by adjusting the rate of phase transition and by application of an electric field. The resulting networks affect the electro-optic performance of liquid crystal devices.