• 한국진공학회지
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• 제18권5호
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• pp.377-383
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• 2009

라디오파 마그네트론 스퍼터링 방법을 사용하여 사파이어 기판 위에 Al 도핑된 ZnO (AZO) 박막을 성장시킨 후에 온도 범위 $600-900^{\circ}C$에서 급속 열처리를 수행하였다. 박막의 결정 구조와 표면 형상은 각각 X-선 회절법과 주사전자현미경으로 조사하였다. 급속 열처리 온도가 증가함에 따라 박막의 결정성은 향상되었고, 평균 50 nm의 크기를 갖는 육각형 형태의 결정 입자가 관측되었다. 증착된 모든 박막은 파장 영역 400-1100 nm에서 92%의 평균 투과율을 나타내었다. 열처리 온도가 증가함에 따라 박막의 밴드갭 에너지는 감소하였고, 광여기 발광 신호의 경우에 자외선 발광 신호의 세기가 감소하면서 400 nm에 중심을 둔 보라색 발광 신호가 주된 피크를 형성하였다. 박막의 전기적 특성은 열처리 온도에 현저한 의존성을 보였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.420-420
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• 2012

ZnO seed layer were deposited on quartz substrate by sol-gel method and prism-like Al-doped ZnO nanorods (AZO nanorods) were grown on ZnO seed layer by hydrothermal method with various Al concentration ranging from 0 to 2.0 at.%. Structural and optical properties of the AZO nanorods were investigated by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), photoluminescence (PL). The diameter of the AZO nanorods was smaller than undoped ZnO nanorods and its diameter of the AZO nanorods decreased with increasing Al concentration. In XRD spectrum, it was observed that stress and full width at half maximum (FWHM) of the AZO nanorods decreased and the 'c' lattice constant increased as the Al concentration increased. From undoped ZnO nanorods, it was observed that the green-red emission peak of deep-level emission (DLE) in PL spectra. However, after Al doping, not only a broad green emission peak but also a blue emission peak of DLE were observed.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.382-382
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• 2012

CIGS thin films have received great attention as a promising material for solar cells due to their high absorption coefficient, appropriate bandgap, long-term stability, and low cost production. CIGS thin films are deposited by various methods such as co-evaporation, sputtering, spray pyrolysis and electro-deposition. The deposition technique is one of the most important processes in preparing CIGS thin film solar cells. Among these methods, co-evaporation is one of the best technique for obtaining high quality and stoichiometric CIGS films. However, co-evaporation method is known to be unsuitable for commercialization. The sputtering is known to be very effective and feasible process for mass production. In this study, CIGS thin films have prepared by rf magnetron sputtering using a $Cu(In_{1-x}Ga_x)Se_2$ single quaternary target without post deposition selenization. This process has been examined by the effects of deposition parameters on the structural and compositional properties of the films. In addition, we will explore the influences of substrate temperature and additional annealing treatment after deposition on the characteristics of CIGS thin films. The thickness of CIGS films will be measured by Tencor-P1 profiler. The crystalline properties and surface morphology of the films will be analyzed using X-ray diffraction and scanning electron microscopy, respectively. The optical properties of the films will be determined by UV-Visible spectroscopy. Electrical properties of the films will be measured using van der Pauw geometry and Hall effect measurement at room temperature using indium ohmic contacts.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.314-314
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• 2012

The dilute magnetic semiconductors (DMS) have been developed to multi-functional electro-magnetic devices. Specially, the Si based DMS formed by ion implantation have strong advantages to improve magnetic properties because of the controllable effects of carrier concentration on ferromagnetism. In this study, we investigated the deep level states of Fe- and Co-ions implanted Si wafer during rapid thermal annealing (RTA) process. The p-type Si (100) wafers with hole concentration of $1{\times}10^{16}cm^{-3}$ were uniformly implanted by Fe and Co ions at a dose of $1{\times}10^{16}cm^{-2}$ with an energy of 60 keV. After RTA process at temperature ranges of $500{\sim}900^{\circ}C$ for 5 min in nitrogen ambient, the Au electrodes with thickness of 100 nm were deposited to fabricate a Schottky contact by thermal evaporator. The surface morphology, the crystal structure, and the defect state for Fe- and Co- ion implanted p-type Si wafers were investigated by an atomic force microscopy, a x-ray diffraction, and a deep level transient spectroscopy, respectively. Finally, we will discuss the physical relationship between the electrical properties and the variation of defect states for Fe- and Co-ions implanted Si wafer after RTA.

• 한국광물학회지
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• 제19권3호
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• pp.189-195
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• 2006

황철석에 대한 압축성 연구를 다이아몬드 앤빌 기기 및 방사광을 이용하고 에너지분산 X-선회절법을 적용하여 상온에서 시행하였다. 황철석의 체적탄성률은 실험조건과 실험기기에 따라 매우 큰 변이를 보이고 있는데 이는 압력전달매체의 특성에 따른 것으로 알려져 있다. $FeS_{2}#1$(황철석+NaCl)과 $FeS_{2}#2$(황철석+MgO)에 대해 압력전달 매체로 각각 NaCl과 유체를 이용하여 체적탄성률 138.9 GPa와 198.2 GPa를 각각 얻었다. 이러한 값은 시료방의 압력상태에 따른 예측 결과치에 대치되는 것으로 그 원인은 압력전달액체의 상변이에 따른 것으로 추정되며 이외에 고상검출기의 차이, E*d값의 차이 등도 영향을 미친 것으로 판단된다. 모든 실험은 포항가속기연구소 1B2 빔라인에서 시행되었다.

• 한국광물학회지
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• 제26권3호
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• pp.175-187
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• 2013

나트로라이트(Na-제올라이트)의 탈수현상에 따른 변화와 특성을 라만 및 X-선 회절실험을 통하여 고온, 동시적인 고온-고압 하에서 특성을 확인하였다. 고온실험은 최고 온도범위에 따라 ${\sim}450^{\circ}C$까지 증온한 XRD 실험에서는 가역적 변화를 관찰하였고, ${\sim}630^{\circ}C$까지 증온한 라만분광실험에서는 포스트라트로라이트로 상전이하는 비가역적인 변화를 관찰하였다. 감온과정 약 $380^{\circ}C$에서 포스트 나트로라이트 상이 나타나는 온도구간을 본 연구에서 새롭게 확인하였다. 동시적인 고온-고압 하(상온 < T < $300^{\circ}C$, 0 GPa < P < 2.1 GPa)에서 나트로라이트 분광선의 이동은 관찰되지 않았다.

• 한국재료학회지
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• 제22권5호
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• pp.249-252
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• 2012

Fe doped $TiO_2$ nanoparticles were prepared under high temperature and pressure conditions by mixture of metal nitrate solution and $TiO_2$ sol. Fe doped $TiO_2$ particles were reacted in the temperature range of 170 to $200^{\circ}C$ for 6 h. The microstructure and phase of the synthesized Fe doped $TiO_2$ nanoparticles were studied by SEM (FE-SEM), TEM, and XRD. Thermal properties of the synthesized Fe doped $TiO_2$ nanoparticles were studied by TG-DTA analysis. TEM and X-ray diffraction pattern shows that the synthesized Fe doped $TiO_2$ nanoparticles were crystalline. The average size and distribution of the synthesized Fe doped $TiO_2$ nanoparticles were about 10 nm and narrow, respectively. The average size of the synthesized Fe doped $TiO_2$ nanoparticles increased as the reaction temperature increased. The overall reduction in weight of Fe doped $TiO_2$ nanoparticles was about 16% up to ${\sim}700^{\circ}C$; water of crystallization was dehydrated at $271^{\circ}C$. The transition of Fe doped $TiO_2$ nanoparticle phase from anatase to rutile occurred at almost $561^{\circ}C$. The amount of rutile phase of the synthesized Fe doped $TiO_2$ nanoparticles increased with decreasing Fe concentration. The effects of synthesis parameters, such as the concentration of the starting solution and the reaction temperature, are discussed.

• 한국분말재료학회지
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• 제23권4호
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• pp.287-296
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• 2016

$Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$ powders have been synthesized in a continuously stirred tank reactor via a co-precipitation reaction between aqueous metal sulfates and NaOH using $NH_4OH$ as a chelating agent. The co-precipitation temperature is varied in the range of $30-80^{\circ}C$. Calcination of the prepared precursors with $Li_2CO_3$ for 8 h at $1000^{\circ}C$ in air results in Li $Ni_{1/3}Co_{1/3}Mn_{1/3}O_2$ powders. Two kinds of obtained powders have been characterized by X-ray diffraction (XRD), scanning electron microscopy, particle size analyzer, and tap density measurements. The co-precipitation temperature does not differentiate the XRD patterns of precursors as well as their final powders. Precursor powders are spherical and dense, consisting of numerous acicular or flaky primary particles. The precursors obtained at 70 and $80^{\circ}C$ possess bigger primary particles having more irregular shapes than those at lower temperatures. This is related to the lower tap density measured for the former. The final powders show a similar tendency in terms of primary particle shape and tap density. Electrochemical characterization shows that the initial charge/discharge capacities and cycle life of final powders from the precursors obtained at 70 and $80^{\circ}C$ are inferior to those at $50^{\circ}C$. It is concluded that the optimum co-precipitation temperature is around $50^{\circ}C$.

• 한국분말재료학회지
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• 제27권5호
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• pp.401-405
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• 2020

Magnesium hydroxide sulfate hydrate (MHSH) whiskers were synthesized via a hydrothermal reaction by using MgO as the reactant as well as the acid solution. The effects of the H₂SO₄ amount and reaction time at the same temperature were studied. In general, MHSH whiskers were prepared using MgSO₄ in aqueous ammonia. In this work, to reduce the formation of impurities and increase the purity of MHSH, we employed a synthesis technique that did not require the addition of a basic solution. Furthermore, the pH value, which was controlled by the H₂SO₄ amount, acted as an important factor for the formation of high-purity MHSH. MgO was used as the raw material because it easily reacts in water and forms Mg⁺ and MgOH⁺ ions that bind with SO₄^2- ions to produce MHSH. Their morphologies and structures were determined using X-ray diffraction (XRD) and scanning electron microscopy (SEM).

• 한국해안해양공학회지
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• 제1권1호
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• pp.71-80
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• 1989

본 연구에서는 무한요소의 개념을 선형파의 회절 및 방사문제에 적용하는 방법에 대해서 연구하였다. 유체의 동압에 의한 하중은 관성력이 중요하다고 가정하여, 점성효과는 무시하였다. 물체 주변의 내부영역은 통상적인 유한요소를 사용하여 모형화하였으며, 외부영역은 특수한 형상함수를 갖는 무한요소로 모형화하였다. 본 연구에서 개발된 무한요소의 형상함수는, 외부영역의 속도포텐셜을 보다 잘 나타내기 위하여, 외부영역의 해를 해석적 고유함수로 표시하였을 때 나타나는 진행파항과 첫번째 산란파항의 점근적인 형태를 사용하여 결정하였으며, 수치해석상의 효율성을 증가시키기 위하여, 무한요소의 시스템행렬 구성시 나타나게 되는 무한방향으로의 적분을 해석적으로 수행하였다. 본 무한요소의 효율성 및 타당성을 입증하기 위하여, 실제 많이 응용되고 있는 연직 축대칭 구조물을 대상으로 수치해석을 수행하였다. 수치해석결과, 아주 적은 수의 요소로 유체영역을 분할했음에도 불구하고, 적분방정식을 이용한 기존의 여러결과들과 아주 잘 일치함을 알 수 있었다. 또한, 해석의 효율성과 해의 정확도에 직접적으로 영향을 주는 무한요소의 위치와 유한요소의 크기에 대한 기준설정을 위한 수치실험도 수행하였다.