• 한국전기전자재료학회논문지
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• 제20권12호
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• pp.1017-1021
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• 2007

To implement tera bit level non-volatile memories of low power and fast operation, proving statistical reproductivity and satisfying reliabilities at the nano-scale are a key challenge. We fabricate the charge trapping nano scaled SONOS unit memories and 64 bit flash arrays and evaluate reliability and performance of them. In case of the dielectric stack thickness of 4.5 /9.3 /6.5 nm with the channel width and length of 34 nm and 31nm respectively, the device has about 3.5 V threshold voltage shift with write voltage of $10\;{\mu}s$, 15 V and erase voltage of 10 ms, -15 V. And retention and endurance characteristics are above 10 years and $10^5$ cycle, respectively. The device with LDD(Lightly Doped Drain) process shows reduction of short channel effect and GIDL(Gate Induced Drain Leakage) current. Moreover we investigate three different types of flash memory arrays.

• 한국전기전자재료학회논문지
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• 제28권4호
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• pp.257-261
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• 2015

In this study, we fabricated a thermoelectric module made of nanoparticles (NPs) and glass fibers investigated its thermoelectric characteristics. P-type HgTe and n-type HgSe NPs synthesized by colloidal method were used as thermoelectric materials and glass fibers were used as spacers between the hot and cold electrodes of the thermoelectric module. In the module, the average Seebeck coefficients of the HgTe and HgSe NPs were 1260 and $-628{\mu}V/K$, respectively. The p-n module generated about a voltage of 11.9 mV and showed a power density of $1.6{\times}10^{-5}{\mu}W/cm^2$ at a temperature difference of 7.5 K.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.21.2-21.2
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• 2009

발광다이오드는 에너지 변환 효율이 높고 친환경적인 장점으로 인하여 차세대 조명용 광원으로 각광받고 있다. 하지만 현재 발광다이오드는 낮은 광추출효율로 인하여 미래의 수요를 충족시킬 수 있을 만큼 충분한 성능의 효율을 나타내지 못하고 있다. 발광다이오드의 낮은 광추출효율은 반도체소재와 외부 공기와의 큰 굴절률 차이로 인하여 발생하는 전반사 현상에 기인한 것으로 이 문제를 해결하기 위하여 발광다이오드 소자의 발광면 및 기판을 텍스처링하는 방법이 중요하게 인식되고 있다. 하지만 현재까지 패턴의 구조에 따른 광추출 특성을 분석한 연구는 미진한 상황이다. 본 연구에서는 임프린팅 및 건식식각 공정을 이용하여 다양한 구조의 나노 및 micron 급 패턴을 발광다이오드의 p-GaN층에 형성하였다. 발광다이오드 기판 위에 하드마스크로 사용하기 위한 SiO2를 50nm 증착한 후 그 위에 UV 임프린팅 공정을 진행하여 폴리머 패턴을 형성시켰다. 임프린팅 공정으로 형성된 폴리머 패턴을 CF4CHF3 플라즈마를 이용하여 SiO2를 건식식각하였고, 이후에 SiCl4와 Ar 플라즈마를 이용한 ICP 식각 공정을 진행하여 p-GaN층을 100nm 식각하였다. 마지막으로 BOE를 이용한 습식식각 공정으로 p-GaN층에 남아있는 SiO2층을 제거하여 p-GaN층에 sub-micron에서 micron급의 홀 패턴을 형성하였다. Photoluminescence(PL) 측정을 통해서 발광다이오드 소자에 형성된 패턴의 구조에 따른 광추출 특성을 분석하였다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.37.2-37.2
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• 2009

다이렉트 프린팅 방식에 대한 수요가 높아지면서 마이크로 노즐에 대한 수요도 높아지고 있다. 마이크로 노즐은 Nano particle deposition system (NPDS)에서 가장 중요한 부분으로 금속이나 세라믹 분말을 음속으로 가속시키는 역할을 한다. 또한 마이크로 노즐은 마이크로 스페이스 셔틀과 주사바늘이 없는 약물 주사 시스템 등의 많은 분야에서 사용 가능하다. 이러한 마이크로 노즐은 대부분 기계적 절삭법을 이용하여 알루미늄으로 만들어져왔다. 하지만 알루미늄으로 만들어진 마이크로 노즐은 경도가 낮아 세라믹 나노 입자를 적층하는 것에 적절치 못하며 사용가능한 수명이 짧다는 단점을 가지고 있다. 또한 가장 큰 단점으로 노즐목을 1mm이하로 제작하는 것이 어렵다는 것이다. 따라서 본 연구에서는 Si wafer를 Deep RIE 방식을 이용하여 3차원적으로 제작하였다. Deep RIE 방식 중 BOSCH process를 이용하였다. 이렇게 만들어진 마이크로 노즐은 다이렉트 프린팅 방식중 하나인 NPDS에 적용하였다. Si wafer로 만들어진 마이크로 노즐이 적용된 NPDS를 이용하여 graphite 분말을 가속하여 적층 실험을 실시하였다 이와 함께 전산 유체 역학(CFD)를 이용하여 마이크로 노즐일 이용한 초음속 가속 가능 여부를 판단하였다. 전산 유체 역학은 유한 요소법을 이용하여 유체의 거동을 시뮬레이션을 통하여 예측하는 것으로 마이크로 노즐 내에서 유체의 흐름을 예상할 수 있다. 실제 실험의 결과와 전산 유체 역학을 이용한 시뮬레이션 결과dml 비교 분석을 실시하였다.

• 한국재료학회지
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• 제24권7호
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• pp.388-392
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• 2014

$Cu_2O$ nanowires were synthesized at large scale on copper plate by thermal oxidation in air. The effect of oxidation time and temperature on the morphology of the nanowires was examined. The oxidation time had no effect on the diameter of the nanowires, while it had a great effect on the density and the length of the nanowires. The density and the length of the nanowires increased, and then decreased, with increasing oxidation time. The oxidation temperature had a tremendous effect on the size-distribution as well as the density of the nanowires. When the oxidation temperature was $700^{\circ}C$, uniform size-distribution and high density of the nanowires was achieved. At lower and higher temperatures, the density of the nanowires was lower, and they displayed a broader size-distribution. It is suggested that the $Cu_2O$ nanowires were grown via a vapor-solid mechanism because no catalyst particles were observed at the tips of the nanowires.

• 한국재료학회지
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• 제30권11호
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• pp.609-614
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• 2020

3 mol% yttria-doped stabilized zirconia (3YSZ) is synthesized by a solvothermal process, and its characteristics are investigated using various methods. Also, the dispersibility of synthesized 3YSZ nanoparticles is observed with the species of surface modifier. The 3YSZ nano sol prepared with an optimum condition is employed in prism coating and its properties are evaluated. The synthesized 3YSZ nanoparticles show a globular shape with about 10 to 20 nm crystallite size. The mixed phases with the nano sol show a high specific surface of 178 ㎡/g. The prism sheet coated with the 3YSZ nano sol present an excellent refractive index, transmittance, and luminance; refractive index is 1.603, transmittance is 90.2 %, and luminance of coating film is improved by 5.9 % compared to that of the film without 3YSZ nano sol. It is verified that the surface modified 3YSZ is suitable as the prism sheet for optical displays.

• 한국재료학회지
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• 제25권10호
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• pp.543-546
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• 2015

$TiO_2$ nanowires were grown by thermal oxidation of TiO powder in an oxygen and nitrogen gas environment at $1000^{\circ}C$. The ratio of $O_2$ to $N_2$ in an ambient gas was changed to investigate the effect of the gas ratio on the growth of $TiO_2$nanowires. The oxidation process was carried out at different $O_2$/$N_2$ ratios of 0/100, 25/75, 50/50 and 100/0. No nanowires were formed at $O_2$/$N_2$ ratios of less than 25/75. When the $O_2$/$N_2$ ratio was 50/50, nanowires started to form. As the gas ratio increased to 100/0, the diameter and length of the nanowires increased. The X-ray diffraction pattern showed that the nanowires were $TiO_2$ with a rutile crystallographic structure. In the XRD pattern, no peaks from the anatase and brookite structures of $TiO_2$were observed. The diameter of the nanowires decreased along the growth direction, and no catalytic particles were detected at the tips of the nanowires which suggests that the nanowires were grown with a vapor-solid growth mechanism.

• 한국재료학회지
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• 제13권8호
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• pp.485-490
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• 2003

We have developed a new way of the constant growth technique to maintain a grating height of originally-etched V-groove of submicron gratings up to 1.5 $\mu\textrm{m}$ thickness by a low pressure metalorganic chemical vapor deposition. The constant growth technique is well performed on two kinds of submicron gratings that made by holography and electron (e)-beam lithography GaAs buffer layer grown on thermally deformed submicron gratings has an important role in recovering the deformed grating profile from sinusoidal to V-shaped by reducing mass transport effects. The thermal deformation effect on submicron gratings made by e-beam lithography is less than that on submicron gratings made by holography. The constant growth technique is an important step to realize complex optoelectronic devices such as one-step grown distributed feedback lasers and two-dimensional photonic crystals.

• 한국재료학회지
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• 제16권6호
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• pp.373-376
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• 2006

[ $Ba(Mg_{1/3}Ta_{2/3})O_3$ ] nanoparticles were synthesized in water solution under mild temperature and pressure conditions by precipitation from $Ba(NO_3),\;Mg(NO_3)_2{\cdot}6H_2O\;and\;TaCl_5$ with aqueous potassium hydroxide. The average size and distribution of the synthesized $Ba(Mg_{1/3}Ta_{2/3})O_3$ nanoparticles were below 100 nm and broad, respectively. The phase of synthesized particles was crystalline reacted at $170^{\circ}C$ for 4 h. The characterization of $Ba(Mg_{1/3}Ta_{2/3})O_3$ nanoparticles were studied using XRD, SEM, and TEM.

• 한국재료학회지
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• 제13권8호
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• pp.550-554
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• 2003

Current nanogold cluster synthesized by chemical routine with 11 or 55 atoms of gold has been widely used for immuno chemistry probe as a form of nanocluster conjugated with biomolecules. It would be an undeveloped region that the 1 nm size of nanogold could be made by materials engineering processing. Therefore, objective of this study is to minimize the size of gold nanocluster as a function of operating temperature and chamber pressure in inert gas condensation (IGC) processing. Evaporation temperature was controlled by input current from 50 A to 65 A. Chamber pressure was controlled by argon gas with a range of 0.05 to 2 torr. The gold nanocluster by IGC was evaluated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The gold nanocluster for TEM analysis was directly sampled with special in-situ method during the processing. Atomic force microscopy (AFM) was used to observe 3-D nanogold layer surfaces on a slide glass for the following biomolecule conjugation step. The size of gold nanoclusters had a close relationship with the processing condition such as evaporation temperature and chamber pressure. The approximately 1 nm size of nanogold was obtained at the processing condition for 1 torr at $1124 ^{\circ}C$.