• 한국결정성장학회지
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• 제26권6호
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• pp.215-219
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• 2016

본 연구에서는 다공성 흑연 캡슐에 Vanadium carbide(VC) 분말을 채워 성장시킨 방법과 SiC 분말과 VC 분말을 혼합하여 다공성 흑연판을 그 위에 덮은 후 성장시키는 방법으로 진행하였으며, 성장된 결정들은 여러 분석방법을 사용하여 각각의 특성들을 관찰하였다. 반절연 SiC 성장은 6H-SiC 종자 결정을 사용하여 PVT(Physical Vapor Transport)법으로 성장을 진행하였다. 반절연으로 성장된 SiC 결정은 XRD를 이용하여 6H-SiC인 것을 확인하였으며, SIMS 분석결과 바나듐 도핑 농도가 바나듐 용해의 한계값 보다 높을 경우 석출물이 발생되며, 결정 품질 저하의 원인이 됨을 확인할 수 있었다.

• 인포메이션 디스플레이
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• 제5권1호
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• pp.25-30
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• 2004

Poly-Si TFT(Thin Film Transistor) technology are reviewed and discussed. Poly-Si TFTs fabricated on glass using low-temperature process were studied extensively for the application to LCD (Liquid Crystal Display) as well as to OLED(Organic Light Emitting Diode) Display. Currently, one of the application targets of the poly-Si TFT is emphasized on the highly functional SOG(System on Glass). Improvement of device characteristics such as an enhancement of carrier mobility has been studied intensively by enlarging the grain size. Reduction of the voltage and shrinkage of the device size are the trend of AM FPD(Active Matrix Flat Panel Display) as well as of Si LSI, which will arise a peculiar issue of uniformity for the device performance. Some approaches such as nucleation control of the grain seed or lateral grain growth have been tried, so far.

• 한국결정학회지
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• 제14권2호
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• pp.73-78
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• 2003

(Ba/sub 1-x/Sr/sub x/)TiO₃ (BST, 0.4< x <0.65) single crystals were successfully grown by the TSSG (Top-Seeded Solution Growth) method, using a commercial [100] SrTiO₃ or as-grown [100] BST single crystals as seed crystals. To obtain the BST single crystals with various compositions x, the Ba/sr molar ratios in the solutions were systematically controlled while the Ti ion content among all cations was fixed at 67 mol%. A linear regression curve between their x values and the molar ratios of Sr/(Ba + Sr) in the solutions could be obtained, which in turn could used to select the initial composition to produce BST crystal with an aimed x value. In addition, the isothermal growth was found more effective for obtaining a compositional uniformity than a slow cooling process.

• 기계저널
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• 제19권4호
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• pp.279-290
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• 1979

Arc Welding의 경우 arc열에 의하여 생성된 용융지(Molten Pool)가 응고하는 과정은 금형주물의 응고과정과 비슷하게 생각되나 실은 응고의 제1단계에서 양자간에 큰 차이가 있다. 즉, 금형에 주입된 용융금속이 응고하는 경우는 금형과 이에 접한 주조금속과는 응고후 별도로 분리할 수 있으며, 양자가 서로 융합해서는 안될 것이다. 이에 반하여 융접의 경우에는 금형속에 있는 용 융금속과 금형이라고 볼 수 있는 모재용융부단면과는 완전히 융합되어야 할 것이다. 금형주조 부분의 응고에서는 금형에 접한 주조금속이 열적과냉각(Thermal Supercooling)을 받아 그 내부에 결정핵이 생성되어 이것이 성장하는 과정을 거칠 것이다. 그러나 융접의 경우에는 일반적으로 용융금속과 모재와는 통일계통의 재료이므로 용융금속에 접한 모재부분 자신이 종자결정(Seed Crystal)와 같은 역할을 하여 용융금속내에 새로히 결정핵을 생성함이 없이 이 위에서 직접 결 정성장이 연행되는 것이다. 이것을 Epitaxial Growth라는 하나 이것이 용접부의 응고에서의 큰 특정인 것이다. 주조, 용접 공히 열절과냉각에 의한 응고의 초기단계를 거치면 합금인 경우 그 후의 응고과정은 주로 조성적 과냉각(Constitutional Supercooling)에 따르게 될 것이다. 이 기 회에 Epitaxy에 관해서 간단히 설명하고저 한다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.184-185
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• 2006

Two-step growth to incorporate the Mg atoms in the ZnO nanorods fabricate by thermal evaporation process and also utilized the ZnO film as a template. In the first step of low temperature, Zn seed metals with low melting temperature formed the droplet, and then MgZnO ternary nanorods were grown by injecting oxygen and evaporating Mg atoms in high temperature process of the second step. The vertical growth of the MgZnO nanorods with large-area distribution and uniformity was successfully performed on the ZnO template. We investigated the shape of the vertically grown 1-D MgZnO nanorods and characterized the optical and crystal properties. We confirmed the incorporation of Mg atoms by the EDS and PL spectrum.

• 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.258-292
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• 1996

In the last year great interest appears to YBCO thin films preparation on different substrate materials. Preparation of epitaxial film is a very difficult problem. There are many requirements to substrate materials that must be fullfilled. Main problems are lattice mismatch (misfit) and similarity of structure. From paper [1] or follows that difference in interatomic distances and angles of substrate and film is mire important problem than similarity of structure. In this work we present interatomic distances and angle relations between substrate materials belonging to ABCO4 group (where A-Sr or Ca, B-rare earth element, C-Al or Ga) of different orientations and YBCO thin films. There are many materials used as substrates for HTsC thin films. ABCO4 group of compounds is characterized by small dielectric constants (it is necessary for microwave applications of HTsC films), absence of twins and small misfit [2]. There most interesting compounds CaNdAlO4, SrLaAlO4 and SrLaGaO4 were investigated. All these compounds are of pseudo-perovskite structure with space group 14/mmm. This structure is very similar to structure of YBCO. SLG substrate has the lowest misfit (0.3%) and dielectric constant. For preparation of then films of substrates of this group of compound plane of <100> orientation are mainly used. Good quality films of <001> orientations are obtained [3]. In this case not only a-a misfit play role, but c-3b misfit is very important too. Sometimes, for preparation of thin films substrates of <001> and <110> orientations were manufactured [3]. Different misfits for different YBCO faces have been analyzed. It has been found that the mismatching factor for (100) face is very similar to that for (001) face so there is possibility of preparation of thin films on both orientations. SrLaAlO4(SLA) and SrLaGaO4(SLG) crystals of general formula ABCO4 have been grown by the Czochralski method. The quality of SLA and SLG crystals strongly depends on axial gradient of temperature and growth and rotation rates. High quality crystals were obtained at axial gradient of temperature near crystal-melt interface lower than 50℃/cm, growth rate 1-3 mm/h and the rotation rate changing from 10-20pm[4]. Strong anisotropy in morphology of SLA and SLG single crystals grown by the Czochralski method is clearly visible. On the basics of our considerations for ABCO4 type of the tetragonal crystals there can appear {001}, {101}, and {110} faces for ionic type model [5]. Morphology of these crystals depend on ionic-covalent character of bonding and crystal growth parameters. Point defects are observed in crystals and they are reflected in color changes (colorless, yellow, green). Point defects are detected in directions perpendicular to oxide planes and are connected with instability of oxygen position in lattice. To investigate facets formations crystals were doped with Cr3+, Er3+, Pr3+, Ba2+. Chromium greater size ion which is substituted for Al3+ clearly induces faceting. There appear easy {110} faces and SLA crystals crack even then the amount of Cr is below 0.3at.% SLG single crystals are not so sensitive to the content of chromium ions. It was also found that if {110} face appears at the beginning of growth process the crystal changes its color on the plane {110} but it happens only on the shoulder part. The projection of {110} face has a great amount of oxygen positions which can be easy defected. Pure and doped SLA and SLG crystals measured by EPR in the<110> direction show more intensive lines than in other directions which allows to suggest that the amount of oxygen defects on the {110} plane is higher. In order to find the origin of colors and their relation with the crystal stability, a set of SLA and SLG crystals were investigated using optical spectroscopy. The colored samples exhibit an absorption band stretching from the UV absorption edge of the crystal, from about 240 nm to about 550 m. In the case of colorless sample, the absorption spectrum consists of a relatively weak band in the UV region. The spectral position and intensities of absorption bands of SLA are typical for imperfection similar to color centers which may be created in most of oxide crystals by UV and X-radiation. It is pointed out that crystal growth process of polycomponent oxide crystals by Czochralski method depends on the preparation of melt and its stoichiometry, orientation of seed, gradient of temperature at crystal-melt interface, parameters of growth (rotation and pulling rate) and control of red-ox atmosphere during seeding and growth (rotation and pulling rate) and control of red-ox atmosphere during seeding and growth. Growth parameters have an influence on the morphology of crystal-melt interface, type and concentration of defects.

• 한국결정성장학회지
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• 제25권2호
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• pp.51-55
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• 2015

본 연구에서는 PVT법으로 4H-SiC 단결정 성장 시 다공성 흑연판을 사용하여 Si/C 비율이나 온도구배, 물질전달의 향상시킴으로써 고품질의 SiC 단결정 기판 제작을 목적으로 연구를 진행하였다. 연구에 사용된 SiC 소스 물질은 흑연 도가니에 넣어 흑연 단열재로 쌓인 구조로 실험을 하였다. 성장온도는 $2100{\sim}2300^{\circ}C$, 그리고 성장압력은 10~30 Torr의 압력으로 아르곤과 질소 분위기에서 성장시켰다. 종자정은 2인치의 $4^{\circ}$ off-axis 4H-SiC의 C면 (000-1)을 사용하였고 다공성 흑연판은 SiC 소스 물질 위에 삽입하였다. 4H-SiC 결정다형 안정화를 위한 C-rich 조건이나 균일한 온도구배를 만들어주기 위해 다공성 흑연판을 삽입하여 실험을 진행하였다. 일반적인 도가니의 경우, 성장된 wafer에서 6H-, 15R-SiC와 같은 다양한 결정다형이 관찰된 반면에 다공성 흑연판을 삽입한 도가니에서는 4H-SiC만 관찰되었다. 또한 다공성 흑연판을 삽입한 도가니에서 성장된 결정에서 MP나 EP의 낮은 결함밀도를 보였으며 결정성 또한 향상된 것을 학인하였다.

• 한국세라믹학회지
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• 제41권10호
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• pp.771-776
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• 2004

Zr을 $8\%$ 첨가한 BZT 세라믹스를 종결정과 소재봉으로 사용하여 floating zone technique법으로 $Ba(Zr_{0.08}Ti_{0.92})O_3$ 다결정을 성장하였다. 열처리 효과를 알아보기 위하여 성장한 결정의 일부를 떼어내어 $1,200^{\circ}C$에서 10시간동안 산소 분위기에서 열처리하였다. $-100^{\circ}C$에서 $+150^{\circ}C$ 온도 영역에서 유전상수 및 유전손실을 10kHz, 100kHz, 그리고 1 MHz에서 측정하여 성장 결정의 유전특성을 알아보았다. 상온($27^{\circ}C$)과 저온($-73^{\circ}C$)에서 직류전장(-15kV/cm$\le$E$\le$15kV/cm)을 인가하면서 유전상수의 변화를 10kHz와 100kHz에서 측정함으로써 유전상수의 전장의존성을 알아보았다. 산소 열처리는 상온에서 10kHz의 튜너빌리티를 $47.5\%$에서 $51\%$로, 그리고 성능지수를 39.6에서 46.4로 향상시키었다. 바이어스 직류전장을 15kV/cm 이상 인가하면 성능지수가 46.4 이상으로 향상될 수 있으므로 이 물질이 마이크로파 전장 조절 소자에 응용될 수 있는 가능성이 있다.

• 한국결정학회지
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• 제1권1호
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• pp.19-28
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• 1990

단결정 6H-SiC는 에너지갭이 3.0eV인 반도체로서 청색발광소자 및 고온반도체소자로 응용이 기대되는 재료이다. 본 연구에서는 청색발광소자 제작을 위해 6H-SiC 단결정을 승화법으로 성장시켰다. 승화법으로 성장시 성장도가니내의 온도구배를 44℃/cm, 성장온도는 1800-1990℃ 압력은 50-1000 mTorr이었다. 사용한 종자정은 에치슨법으로 성장시킨 SiC 단결정을 사용하였다. 성장된 6H-SiC 결정은 종자징위에 epitaxial growtll를 하였음을 편광현미경과 Back reflection Xray Laue 법으로 확인하였다. 성장조건을 변화시켰을 때 생성되는 결정상의 변화를 XRD로 조사하였다. 성장 온도가 1840℃ 이상일 경우에는 6H-SiC이 성장되었으며, 그 이하에서는 6H-SiC가 성장되었다. 또한 3C-SiC는 저온 저파포화도 성장조건에서 성장되는 상임을 확인하였다. van der Pauw측정법에의한 전기적 특성을 조사하였는데, 전도형은 p형이고 hole 농도와 이동도는 7.6x1014cm-3와 19cm2 V-1sec-1였다.

• Current Photovoltaic Research
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• 제2권3호
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• pp.103-109
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• 2014

Highly efficient hydrogenated nanocrystalline silicon (nc-Si:H) thin-film solar cells were prepared on flexible stainless steel substrates using plasma-enhanced chemical vapor deposition. To enhance the performance of solar cells, material properties of back reflectors, n-doped seed layers and wide bandgap nc-SiC:H window layers were optimized. The light scattering efficiency of Ag back reflectors was improved by increasing the surface roughness of the films deposited at elevated substrate temperatures. Using the n-doped seed layers with high crystallinity, the initial crystal growth of intrinsic nc-Si:H absorber layers was improved, resulting in the elimination of the defect-dense amorphous regions at the n/i interfaces. The nc-SiC:H window layers with high bandgap over 2.2 eV were deposited under high hydrogen dilution conditions. The vertical current flow of the films was enhanced by the formation of Si nanocrystallites in the amorphous SiC:H matrix. Under optimized conditions, a high conversion efficiency of 9.13% ($V_{oc}=0.52$, $J_{sc}=25.45mA/cm^2$, FF = 0.69) was achieved for the flexible nc-Si:H thin-film solar cells.