• 한국진공학회지
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• 제9권4호
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• pp.400-405
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• 2000

유기금속 소스의 농도를 연속적으로 in-situ 측정이 가능한 EPISON ultrasonic monitor를 이용하여 TMIn(trimethly-indium)의 소스 고갈이 InGaAs, InGaAsP bulk 에피층과 1.55 $mu extrm{m}$ InGaAs/InGaAsP SMQW (strained multi-quantum well)에 미치는 영향을 조사하였다. TMIn 소스는 사용량이 80%에서 급격하게 소스 고갈 현상을 보였다. TMIn 소스는 사용량이 80%에서 급격하게 소스 고갈 현상을 보였다. TMIn 소스 고갈에 의한 에피층의 특성 변화를 조사한 결과, bulk 에피층의 경우에는 소스가 고갈 되기 전에 성장한 에피층과 비교하여 DCXRD(double crystal X-ray diffractometry) spectrum에서 피크 분리가 약 300 arcsec정도 Ga-rich 방향으로 이동하였으며 relative FWHM은 약 2배 가량 증가하는 것을 보였다. SMQW 구조에서는 bulk 에피층과는 달리, PL 중심파장에서도 약 40 nm 정도 단파장쪽으로 이동하였으며, 피크 분리는 약 300 arcsec정도 Ga-rich 방향으로 이동하였다. 하지만, EPISON의 closed loop 기능을 사용할 경우에는 TMIn 소스 사용량이 95%에서도 피크 분리가 $\pm$100 arcsec이내의 재현성 있는 에피층 성장이 가능하다는 것을 알 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1998년도 제14회 학술발표회 논문개요집
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• pp.110-110
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• 1998

GaN는 직접천이형 에너지 캡을 가지며 In과 화합물을 형성할 경우 1.geV-3.4eV까지 다양한 에너지 캡을 가지므로 청색 발광소자 고출력소자 고온 전자소자둥 웅용성이 많 은 물절로서 각광을 받고 있다. 그러나 G랴‘에 적합한 기판이 없다는 문제점으로 인하여 F FET, LD와 같은 다양한 구조의 웅용에 제 약이 따랐다. 이에 본 연구에서는 RF(radio frequency) Plasma-Assisted MBE( molecular beam e epitaxy )를 이용하여 InxGaj xN/G암J 양자우물 구조를 성장하였다. 이렇게 성장된 I InxGaj xN 박막과 InxGaj xN/GaN 양자우물구조의 특성의 분석은 광학적 특성올 PL( p photoluminescence ) , 결 정 성 의 분석 은 XRD ( x-ray diffraction ), 표면 과 단변 의 계 변 특성은 SEM(scanning electron microscopy)을 이용하여 분석하였다. 저온 PL의 측정결 과 기판온도를 680$^{\circ}$C로 고정한 후 In cell의 온도를 650$^{\circ}$C에서 775$^{\circ}$C까지 증가함에 따라 I InxGaj xN에 관계된 피크위치가 약3이neV정도 red shift 함을 관찰할 수 있었다. 한편 I InxGaj xN/GaN 양자우물구조의 경우 PL피크가 3.2없eV로써 InxGaj- xN의 PL 피크에 비 해 에서 약 25me V 고에너지 이동이 관측되었으며 이것은 우불 내에서 에너지레벨의 c confinement효과에 의해 에너지의 변화에 의한 것엄올 확인하였으며, 양자우물 구조에서 우물의 두께를 줄임에 따라 변화 폭은 1이neV정도 고에너지 이동을 관찰할 수 있었다. X XRD 측정의 결과 In의 mole fraction에 따라 격자상수의 변화를 관찰하였으며, 결정 성의 변화를 피크의 세기로 관찰하였다 .. XRD로 판단한 In의 mole fraction은 0.2임을 알 았다 .. SEM 측정은 표변과 단면의 측정으로서 표연특성과 단면의 특성을 InxGaj xN, I InxGaj xN/GaN 양자우물 구조 모두 알아보았다. 측정 결과 InxGaj-xN의 성 장조건으로 기판온도가 낮아지면서 표면의 거칠기 정도가 증가하였으며,680$^{\circ}$C의 기판온도에서 성장 한 양자우물 구조에 있어서 매끄라운 표면올 얻올 수 있었다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.619-619
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• 2009

Recently, silica nanostructures are widely used in various applicationary areas such as chemical sensors, biosensors, nano-fillers, markers, catalysts, and as a substrate for quantum dots etc, because of their excellent physical, chemical and optical properties. Additionally, these days, semiconductor silica and silicon with high purity is a key challenge because of their metallurgical grade silicon (MG-Si) exhibit purity of about 99% produced by an arc discharge method with high cast. Tremendous efforts are being paid towards this direction to reduce the cast of high purity silicon for generation of photovoltaic power as a solar cell. In this direction, which contains a small amount of impurities, which can be further purified by acid leaching process. In this regard, initially the low cast rice-husk was cultivated from local rice field and washed well with high purity distilled water and were treated with acid leaching process (1:10 HCl and $H_2O$) to remove the atmospheric dirt and impurity. The acid treated rice-husk was again washed with distilled water and dried in an oven at $60^{\circ}C$. The dried rice-husk was further annealed at different temperatures (620 and $900^{\circ}C$) for the formation of silica nanospheres. The confirmation of silica was observed by the X-ray diffraction pattern and X-ray photoelectron spectroscopy. The morphology of obtained nanostructures were analyzed via Field-emission scanning electron microscope(FE-SEM) and Transmission electron microscopy(TEM) and it reveals that the size of each nanosphares is about 50-60nm. Using the Inductively coupled plasma mass spectrometry(ICP-MS), Silica was analyzed for the amount of impurities.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.441-441
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• 2011

$TiO_2$ nanoparticles were grown on carbon fiber by atomic later deposition (ALD) with TTIP $(Ti(OCH(CH_3)_2)_4$ and $H_2O$ precusors. After sampe surfaces were treated by electron beam (1 MeV, 5 KGy), an improvement in the photocatalytic reacitivity of $TiO_2$ nanoparticles on carbon fiber was observed. An increase in the population of hydroxyl group on $TiO_2$ particles and the oxidation of carbon fiber were found upon e-beam exposure, whereas there was no noticeable changes of their morphology. It implies that those changes in O and C 1s state of $TiO_2$ particles/carbon fiber induced by e-beam treatment could be related to the enhancement of the photocatalytic activity. In contrast, when carbon fiber fully covered with $TiO_2$ thick films was treated with high-energy electron beam under same conditions, the improvement of photocatalytic activity as well as any changes in XPS spectra (Ti 2p, O 1s and C 1s) could not be found.

• Journal of Korean Vacuum Science & Technology
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• 제4권2호
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• pp.47-49
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• 2000

We report on the fabrication and characterization of InGaN/GaN multiple quantum well light emitting diode (LED) with a highly transparent Pt ohmic contact as a current spreading layer. The value of light transmittance of a Pt thin film with a thickness of 8 m on p-GaN was measured to be 85% at 450nm. The peak wavelength and the full-width at half-maximum (FWHM) of the emission spectrum of the LED at 20 mA were 453 m and 23 m, respectively. Pt-contacted LEDs show good electrical properties and high light-output efficiency compared to Ni/Au-contacted ones. These results suggest that a Pt thin film can be used as an effective current spreading layer with high light-transparency.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.183-183
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• 2011

Multiferroic materials have been widely studied in recent years, because of their abundant physics and potential applications in the sensors, data storage, and spintronics. $BiFeO_3$ is one of the well-known single-phase multiferroic materials with $ABO_3$ structure and G-type antiferromagnetic behavior below the Neel temperature $T_N$ ~ 643 K, but the ferroelectric behavior below the Curie temperature $T_c$~1,103 K. In this study, the $BiFe_{1-x}Ni_xO_3$ (x=0 and 0.05) bulk ceramics were prepared by solid-state reaction and rapid sintering with high-purity $Bi_2O_32$, $Fe_3O_4$ and NiO powders. The powders of stoichiometric proportions were mixed, as in the previous investigations, and calcined at 450$^{\circ}C$ for $BiFe_{1-x}Ni_xO_3$ for 24 h. The obtained powders were grinded, and pressed into 5-mm-thick disks of 1/2-inch diameter. The disks were directly put into the oven, which has been heated up to 800$^{\circ}C$ and sintered in air for 20 min. The sintered disks were taken out from the oven and cooled to room temperature within several min. The phase of samples was checked at room temperature by powder x-ray diffraction using a Rigaku Miniflex diffractometer with Cu K${\alpha}$ radiation. The Raman measurements were carried out by employing a hand-made Raman spectrometer with 514.5-nm-excitation $Ar^+$ laser source under air ambient condition on a focused area of 1-${\mu}m$ diameter. The field-dependent magnetization measurements were performed with a superconducting quantum-interference-device magnetometer.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.48-48
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• 2011

We have developed a chemically-driven top-down approach using vapor phase HCl to form various GaN nanostructures and successfully demonstrated dislocation-free and strain-relaxed GaN nanostructures without etching damage formed by a selective dissociation method. Our approach overcomes many limitations encountered in previous approaches. There is no need to make a pattern, complicated process, and expensive equipment, but it produces a high-quality nanostructure over a large area at low cost. As far as we know, this is the first time that various types of high-quality GaN nanostructures, such as dot, cone, and rod, could be formed by a chemical method without the use of a mask or pattern, especially on the Ga-polar GaN. It is well known that the Ga-polar GaN is difficult to etch by the common chemical wet etching method because of the chemical stability of GaN. Our chemically driven GaN nanostructures show excellent structure and optical properties. The formed nanostructure had various facets depending on the etching conditions and showed a high crystal quality due to the removal of defects, such as dislocations. These structure properties derived excellent optical performance of the GaN nanostructure. The GaN nanostructure had increased internal and external quantum efficiency due to increased light extraction, reduced strain, and improved crystal quality. The chemically driven GaN nanostructure shows promise in applications such as efficient light-emitting diodes, field emitters, and sensors.

• 원예과학기술지
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• 제35권1호
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• pp.21-29
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• 2017

This study was conducted to determine the effects of artificial lighting sources on vegetative growth of Phalaenopsis and Doritaenopsis (an intergeneric hybrid of Doritis and Phalaenopsis) orchids. One - month - old plants were cultivated under fluorescent lamps, cool - white light - emitting diodes (LEDs), or warm - white LEDs at 80 and $160{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$. The blue (400 - 500 nm) : green (500 - 600 nm) : red (600 - 700 nm) : far - red (700 - 800 nm) ratios of the fluorescent lamps, cool-white LEDs, and warm-white LEDs were 1 : 1.3 : 0.8 : 0.1, 1 : 1.3 : 0.6 : 0.1, and 1 : 2.7 : 2.3 : 0.4, respectively. Each light treatment was maintained for 16 weeks in a closed plant-production system maintained at $28^{\circ}C$ with a 12 h photoperiod. The longest leaf span, as well as the leaf length and width of the uppermost mature leaf, were observed in plants treated with warm-white LEDs. Plants grown under fluorescent lamps had longer and wider leaves with a greater leaf span than plants grown under cool-white LEDs, while the maximum quantum efficiency of photosystem II was higher under cool-white LEDs. The vegetative responses affected by different lighting sources were similar at both 80 and $160{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$. Leaf span and root biomass were increased by the higher light intensity in both cultivars, while the relative chlorophyll content was decreased. These results indicate that relatively high intensity light can promote vegetative growth of young Phalaenopsis plants, and that warm - white LEDs, which contain a high red-light ratio, are a better lighting source for the growth of these plants than the cool-white LEDs or fluorescent lamps. These results could therefore be useful in the selection of artificial lighting to maximize vegetative growth of Phalaenopsis plants in a closed plant - production system.

• Nuclear Engineering and Technology
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• 제45권5호
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• pp.683-688
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• 2013

Candidate coating materials for re-usable metallic nuclear fuel crucibles, TaC, TiC, ZrC, $ZrO_2$, and $Y_2O_3$, were plasmasprayed onto a niobium substrate. The microstructure of the plasma-sprayed coatings and thermal cycling behavior were characterized, and U-Zr melt interaction studies were carried out. The TaC and $Y_2O_3$ coating layers had a uniform thickness, and high density with only a few small closed pores showing good consolidation, while the ZrC, TiC, and $ZrO_2$ coatings were not well consolidated with a considerable amount of porosity. Thermal cycling tests showed that the adhesion of the TiC, ZrC, and $ZrO_2$ coating layers with niobium was relatively weak compared to the TaC and $Y_2O_3$ coatings. The TaC and $Y_2O_3$ coatings had better cycling characteristics with no interconnected cracks. In the interaction studies, ZrC and $ZrO_2$ coated rods showed significant degradations after exposure to U-10 wt.% Zr melt at $1600^{\circ}C$ for 15 min., but TaC, TiC, and $Y_2O_3$ coatings showed good compatibility with U-Zr melt.

• 한국광학회지
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• 제17권6호
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• pp.564-568
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• 2006

반도체 광증폭기에 기반을 둔 이득포화특성을 이용하여 XOR, AND, OR 논리 게이트를 동시에 구현하는 다기능 전광 논리소자를 설계하고 구현하였다. 상용화된 프로그램인 VPI Component $Maker^{TM}$을 사용하여 시뮬레이션을 수행하였고 10 Gbit/s의 입력 신호를 사용하여 XOR, AND, OR 논리동작을 동시에 구현하는 다기능 전광 논리소자를 구현하였다.