• 한국결정성장학회지
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• 제12권3호
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• pp.138-143
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• 2002

본 연구에서는 용액합성법(solution synthesis technique)에 의해 ZnS : Cu nano 입자를 합성하였고, 결정구조 및 입자형상 등의 구조적 특성과, 광흡수/투과 특성, 에너지밴드갭, 그리고 photoluminescence(PL) 여기 및 발광 특성 등의 광학적 특성을 분석하였다. 일반적인 용액상태의 화학적 합성 방법과는 달리 합성온도를 $80^{\circ}C$로하였으며, sulfur의 precursor로 thiourea를 채택하여 Cu 도핑의 용이성을 구현하였다. 합성된 undoped ZnS 와 ZnS : Cu nano 입자는 모두 cubic 구조를 가졌으며 구형입자로 합성되었고, 광흡수단의 위치도 모두 ~305 nm에 나타나서 양자사이즈효과가 발생하였음을 알 수 있었다. PL 발광강도와 반가폭은 Cu 도핑농도가 0.03M 일 때 각각 최고치와 최저치를 나타냈는데, 이와 같이 용액합성법에 의해 합성된 ZnS : Cu 에서 Cu 의 농도변화에 따른 PL 스펙트럼의 강도와 반가폭의 변화는 본 연구에서 최초로 보고되는 것이다. 광흡수단 측정 및 PL 여기 실험결과, 본 연구의 주된 발광피크인 ~510 nm 발광밴드는 Cu에 의해 에너지밴드갭 내에 형성된 발광재결합센터를 통한 것임을 알 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.251-252
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• 2012

Recently, the growing interest in organic microelectronic devices including OLEDs has led to an increasing amount of research into their many potential applications in the area of flexible electronic devices based on plastic substrates. However, these organic devices require a gas barrier coating to prevent the permeation of water and oxygen because organic materials are highly susceptible to water and oxygen. In particular, high efficiency OLEDs require an extremely low Water Vapor Transition Rate (WVTR) of $1{\times}10^{-6}g/m^2$/day. The Key factor in high quality inorganic gas barrier formation for achieving the very low WVTR required ($1{\times}10^{-6}g/m^2$/day) is the suppression of defect sites and gas diffusion pathways between grain boundaries. In this study, we developed an $Al_2O_3$ nano-crystal structure single gas barrier layer using a Neutral Beam Assisted Sputtering (NBAS) process. The NBAS system is based on the conventional RF magnetron sputtering and neutral beam source. The neutral beam source consists of an electron cyclotron Resonance (ECR) plasma source and metal reflector. The Ar+ ions in the ECR plasma are accelerated in the plasma sheath between the plasma and reflector, which are then neutralized by Auger neutralization. The neutral beam energies were possible to estimate indirectly through previous experiments and binary collision model. The accelerating potential is the sum of the plasma potential and reflector bias. In previous experiments, while adjusting the reflector bias, changes in the plasma density and the plasma potential were not observed. The neutral beam energy is controlled by the metal reflector bias. The NBAS process can continuously change crystalline structures from an amorphous phase to nano-crystal phase of various grain sizes within a single inorganic thin film. These NBAS process effects can lead to the formation of a nano-crystal structure barrier layer which effectively limits gas diffusion through the pathways between grain boundaries. Our results verify the nano-crystal structure of the NBAS processed $Al_2O_3$ single gas barrier layer through dielectric constant measurement, break down field measurement, and TEM analysis. Finally, the WVTR of $Al_2O_3$ nano-crystal structure single gas barrier layer was measured to be under $5{\times}10^{-6}g/m^2$/day therefore we can confirm that NBAS processed $Al_2O_3$ nano-crystal structure single gas barrier layer is suitable for OLED application.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.65-65
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• 2003

Chemical mechanical polishing (CMP) is one of the most important processes in recent ULSI (Ultra Large Scale Integrated Circuit) manufacturing technology. Recently, ceria slurries with surfactant have recently been used in STI-CMP,[1] became they have high oxide-to-nitride removal selectivity and widen the processing margin The role of the abrasives, however, on the effect of planarization on STI-CMP is not yet clear. In this study, we investigated how the crystal characteristic affects the planarization efficiency of wafer surface with controlling crystallite size and poly crystalline abrasive size independently.

• 한국결정성장학회지
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• 제17권4호
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• pp.172-178
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• 2007

수평회전식 수열법에 의해 운모 분말을 합성하였다. 수열조건은 출발원료로 $K_2O,\;Al(OH)_3$ 그리고 $SiO_2$의 비는 1 : 3 : 3mol%로 하고 수열용매로 8mol%의 KOH를 함께 추가하여 $260^{\circ}C$에서 72시간 동안 반응시켰다. 합성한 분말은 수직형 수열처리법에 의한 은나노 코팅 운모 제조를 위해 사용하였다. 은나노 코팅의 처리를 위한 수열조건은 출발원료로 합성한 분말로 하고, 수열용매로 $0.5{\ell}$ 3차 증류수, 그리고 1,000ppm의 은나노 졸을 코팅원료로 사용하여 $160{\sim}260^{\circ}C$ 범위에서 72시간 동안 반응시켰다. 처리 후 결정구조, 은나노 코팅 여부 및 코팅된 운모의 특성은 XRD, SEM, TEH-EDX 및 shake plask법을 통해 분석하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.253-253
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• 2012

The effects of oxidation on the order-disorder transition in NiPt bimetallic alloy crystal have been investigated using in-situ synchrotron x-ray scattering technique. The temperature dependence of the crystal structure and the order parameter were measured during in-situ heating and cooling under vacuum and oxygen environments. The order-disorder transition temperature of NiPt alloy crystals in vacuum was between $615^{\circ}C$ and $627^{\circ}C$. On the other hand under oxygen environment, the transition temperature decreases by about $31^{\circ}C$ after the oxidation. The change of the transition temperature can be explained by the formation of NiO crust on the surface of NiPt crystal, which alters the composition of the Ni and Pt atoms. Since the transition temperature depends sensitively on the Ni-Pt composition, the transition temperature changes as Ni atoms diffuse out to form NiO.

• Bulletin of the Korean Chemical Society
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• 제29권4호
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• pp.817-821
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• 2008

We have investigated the influence of the crystal structure on the chemical bonding nature and photocatalytic activity of cubic and hexagonal perovskite A[$Cr_{1/2}Ta_{1/2}$]O3 (A = Sr, Ba) compounds. According to neutron diffraction and field emission-scanning electron microscopy, the crystal structure and particle size of these compounds are strongly dependent on the nature of A-site cations. Also, it was found that the face-shared octahedra in the hexagonal phase are exclusively occupied by chromium ions, suggesting the presence of metallic (Cr-Cr) bonds. X-ray absorption and diffuse UV-vis spectroscopic analyses clearly demonstrated that, in comparison with cubic Sr[$Cr_{1/2}Ta_{1/2}$]$O_3$ phase, hexagonal Ba[$Cr_{1/2}Ta_{1/2}$]$O_3$ phase shows a decrease of Cr oxidation state as well as remarkable changes in interband Cr d-d transitions, which can be interpreted as a result of metallic (Cr-Cr) interactions. According to the test of photocatalytic activity, the present semiconducting materials have a distinct activity against the photodegradation of 4-chlorophenol. Also the Srbased compound was found to show a higher photocatalytic activity than the Ba-based one, which is attributable to its smaller particle size and its stronger absorption in visible light region.

• 한국결정성장학회지
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• 제22권1호
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• pp.1-4
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• 2012

O- and Zn-polar ZnO films were grown by DC magnetron sputtering. Growth of high-quality, single-crystal ZnO thin films were confirmed by XRD and pole figure analysis. O-polar ZnO was grown on an $Al_2O_3$ substrate, which was confirmed by a slow growth rate (378 nm/hr), a fast etching rate (59 nm/min), and by the hillocks on the surface after etching. Zn-polar ZnO was grown on a GaN/$Al_2O_3$ substrate, which was confirmed by a fast growth rate (550 nm/hr), a slow etching rate (28 nm/min), and by pits on the surface after etching. Results from the present study show that it is possible to use DC-sputtering to grow ZnO film with the same polarity as other epitaxial growth methods.

• Transactions on Electrical and Electronic Materials
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• 제11권3호
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• pp.134-137
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• 2010

We have proposed a transflective liquid crystal display (LCD) driven by the fringe field using a liquid crystal (LC) with a negative dielectric anisotropy. The device used different twist angles of the liquid crystals (LC) in the transmissive (T) and the reflective (R) regions when voltage is applied. With the optimization of the pixel electrode width and the distance between them, the LC directors in the R- and T-regions can be rotated by about $22.5^{\circ}$ and $45^{\circ}$ on an average, respectively. As a result, a high image quality transflective LCD with a single gap, a single gamma, and a wide viewing angle characteristics in both the R- and T- regions can be realized.

• 한국전기전자재료학회논문지
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• 제19권3호
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• pp.267-272
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• 2006

Optical waveguide based on symmetric and asymmetric Mach-Zehnder interferometer(MZI) type was designed, fabricated and measured the optical characteristics for the application of biosensor. The wavelength of the input optical signal for the device was 1550 nm. And the difference of refractive index was $0.45\;{\Delta}\%$ between core and cladding of the device. The TM(Transverse Magnetic) mode optical properties of the biosensor were analyzed with the refractive index variation of gold thin film deposited for overclad. Nowadays, nano-photonic crystal structures have been paied much attention for its high optical sensitivity. There is a technique to realize the structure, which is called Dip-Pen Nanolithography(DPN) process. The process requires a nano-scale process patterning resolution and high reliability. In this paper, two dimensional nano-photonic crystal array on the surface was proposed for improving the sensitivity of optical biosensor. And the Dip-Pen Nanolithogrphy process was investigated to realize it.

• 한국결정성장학회지
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• 제26권2호
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• pp.74-79
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• 2016

기계적 강도가 우수한 부분안정화 지르코니아(3 mol% Yttria Partially Stabilized Zirconia) 세라믹스의 정전기 방지를 목적으로 LSM 복합 세라믹을 제조하는 과정에서 소결체 표면에서 란타늄산화물을 주조성으로 하는 나노로드의 성장을 확인하였다. 성장조건에 따라 나노로드의 직경 및 종횡비가 크게 변화하였으며, 광학현미경으로 관찰한 결과 입사광의 집속현상으로 밝게 빛나는 나노로드를 확인하였다. SEM 및 TEM으로 관찰한 결과, La를 주성분으로 하며 Sr, Mn 그리고 Si 등이 미량 첨가된 산화물임을 확인하였고, 이들의 외형으로부터 결정상이 잘 발달된 것을 확인하였다.