• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권2호
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• pp.78-81
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• 2000

The closed-form analytic solutions for the breakdown voltage of 6H-SiC RTD(silicon carbide reachthrough diode) having metal$-n^--n^+$ Schottky structure or $p^+-n^--n^+$, are successfully derived by solving impact ionization integral using an effective ionization coefficient. For the lightly doped n- epitaxial layer, the breakdown voltage of SiC RTD are nearly constant with the increased doping concentration while the breakdown voltages decrease for the heavily doped epitaxial layer.

• 동력기계공학회지
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• 제4권4호
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• pp.99-107
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• 2000

In this study several P type and N type ceramic semiconductors were prepared by atomic valence control and their electric resistivities were investigated with various concentrations of additive impurities. N-P junctions were made by thin film printing method and their varistor-like characteristics were investigated and their availability was discussed. The results are followings, 1) Some N type semiconductors with a proper concentration of additive impurity have minimum resistivities. 2) The N-P junction samples with ZnO as a constituent material of N type semiconductor have linearity in voltage-current characteristics, but the other N-P junction samples have the non-linearity, 3) Some N-P junction samples showed the good varistor-like characteristics.

• Bulletin of the Korean Chemical Society
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• 제28권7호
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• pp.1119-1126
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• 2007

Hydrogen gas and carbon nanotubes along with nanocarbon were produced from commercial natural gas using fixed bed catalyst reactor system. The maximum amount of carbon (491 g/g of catalyst) formation was achieved on 25% Ni, 3% Cu supported catalyst without formation of CO/CO2. Pure carbon nanotubes with length of 308 nm having balloon and horn type shapes were also formed at 673 K. Three sets of catalysts were prepared by varying the concentration of Ni in the first set, Cu concentration in the second set and doping with K in the third set to investigate the effect on stabilization of the catalyst and production of carbon nanotubes and hydrogen by copper and potassium doping. Particle size analysis revealed that most of the catalyst particles are in the range of 20-35 nm. All the catalysts were characterized using powder XRD, SEM/EDX, TPR, CHN, BET and CO-chemisorption. These studies indicate that surface geometry is modified electronically with the formation of different Ni, Cu and K phases, consequently, increasing the surface reactivity of the catalyst and in turn the Carbon nanotubes/H2 production. The addition of Cu and K enhances the catalyst dispersion with the increase in Ni loadings and maximum dispersion is achieved on 25% Ni: 3% Cu/Al catalyst. Clearly, the effect of particle size coupled with specific surface geometry on the production of hydrogen gas and carbon nanotubes prevails. Addition of K increases the catalyst stability with decrease in carbon formation, due to its interaction with Cu and Ni, masking Ni and Ni:Cu active sites.

• 한국결정성장학회지
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• 제25권2호
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• pp.68-73
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• 2015

$Yb^{3+}$ 이온이 25 at.%까지 치환된 $Y_3Al_5O_{12}$ 단결정을 Czochralski 법으로 성장시켰다. 0.8 mm/h의 인상속도와 10 rpm의 회전 속도로 40 mm의 결정 직경과 160 mm의 결정 길이를 가진 단결정을 얻었다. 결정 성장 분위기는 순수한 질 소 혹은 질소와 산소를 혼합한 가스 분위기였다. 순수한 질소 분위기에서는 청록색을 띤 결정이 성장되었고 99 %의 질소와 1 %의 산소를 혼합한 가스 분위기에서 성장한 결정은 무색이었다. 농도 분석결과를 보면, 결정의 길이가 길어짐에 따라 $Yb^{3+}$의 농도는 감소하고, core 영역의 $Yb^{3+}$ 농도는 core 없는 영역보다 다소 높게 검출되었다. $Yb^{3+}$ 이온의 도핑 농도가 증가함에 따라 형광 수명은 감소하였다.

• Advances in environmental research
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• 제5권1호
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• pp.61-77
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• 2016

$NanoTiO_2$ was synthesized by ultrasonication assisted sol-gel process and subjected to iron doping and carbon-iron codoping. The synthesized catalysts were characterized by XRD, HR-SEM, EDX, UV-Vis absorption spectroscopy and BET specific surface area analysis. The average crystallite size of pure $TiO_2$ was in the range of 30 - 33 nm, and that of Fe-$TiO_2$ and C-Fe $TiO_2$ was in the range of 7 - 13 nm respectively. The specific surface area of the iron doped and carbon-iron codoped nanoparticles was around $105m^2/g$ and $91m^2/g$ respectively. The coupled semiconductor photo-Fenton's activity of the synthesized catalysts was evaluated by the degradation of a cationic dye (C.I. Basic blue 9) and an anionic dye (C.I. Acid orange 52) with concurrent investigation on the operating variables such as pH, catalyst dosage, oxidant concentration and initial pollutant concentration. The most efficient C-Fe codoped catalyst was found to effectively destruct synthetic dyes and potentially treat real textile effluent achieving 93.4% of COD removal under minimal solar intensity (35-40 kiloLUX). This reveals the practical applicability of the process for the treatment of real wastewater in both high and low insolation regimes.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.171-171
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• 2010

GaN 기반 Light emitting diodes(LEDs)의 p-type doping layer는 일반적으로 hole을 발생시키는 acceptor로 Mg이 사용하되고 있다. 보통 Mg이 도핑된 p-type GaN은 >$1\;{\Omega}{\cdot}cm$의 저항이 존재하는데 그 이유는 Mg의 열적 이온화를 위한 activation 에너지가 높아서 상온에서 valence band의 hole concentration는 전체 억셉터 농도의 1%가 되지 않기 ��문이다. 본 논문에서는 높은 hole 농도를 얻기 위해서 metalorganic chemical-vapor deposition (MOCVD)를 장비를 사용하여 사파이어 기판의 misorientation-angle에 따른 p-type a-plane(11-20) GaN 특성을 분석하였다. misorientation-angle은 c축 방향으로 $+0.15^{\circ}$, $-0.15^{\circ}$, $-0.2^{\circ}$, $-0.4^{\circ}$ off된 r-plane(1-102) 사파이어 기판 을 사용하였다. p-type 도핑물질로 bis-magnesium (Cp2Mg) 소스를 사용하였고 성장 과정중 발생하는 hydrogen passivation으로 인한 Mg-H complexes현상을 해결하기위해 conventional furnace annealing (CFA)와 rapid thermal annealing (RTA)를 이용하여 열처리 공정을 진행하였다. 열처리 공정은 Air와 N2 분위기에서 $650^{\circ}C$에서 $900^{\circ}C$ 사이의 다양한 온도에서 수행하였고 Hall 측정을 위해 Ni을 전극 물질로 사용하였다. 상온에서 Accent HL5500IU Hall system을 사용하여 hole concentration, mobility, specific resistance을 측정하였다. 열처리 공정 후 Hall측정 결과 $+0.15^{\circ}$, $-0.15^{\circ}$, $-0.2^{\circ}$, $-0.4^{\circ}$ off된 각 샘플들은 온도, 시간, 분위기에 따라 hole concentration ($7.4{\times}10^{16}cm^{-3}{\sim}6{\times}10^{17}cm^{-3}$), mobility(${\mu}h=\;1.72\;cm^2/V-s\;{\sim}15.2\;cm^2/V-s$), specific resistance(4.971 ohm-cm ~8.924 ohm-cm) 가 변화됨을 확인 할 수 있었다. 또한 광학적 특성을 분석하기 위해 Photoluminescence (PL)을 측정하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.192-195
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• 2000

Antimony doped tin oxyde thin films have been deposited by sol-gel method using non-alkoxide precursor SnCl$_2$$.$2H$_2$O as host and SbC1$_3$ as dopant material. Using spin coating method, thin films of thickness up to 200nm have been uniformly deposited on Corning 1737F non-alkali glass substrates. Effect of Sb doping concentration and heat treatment on electrical and optical properties was investigated. Heat treatment was performed at the temperature from 350$^{\circ}C$ to 650$^{\circ}C$ in flowing O$_2$. The resulting ATO films showed widely changing electrical resistivity and optical transmittance values in the visible spectrum depending on the composition and firing condition.

• 한국결정성장학회지
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• 제7권3호
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• pp.393-399
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• 1997

승화법에 의한 6H-SiC 단결정의 최적 성장조건을 설정하여 고품질의 6H-Sic 단결정을 성장하였다. 성장된 결정의 직경은 약 33 mm, 길이는 약 11 mm였다. 성장된 결정을 절단하여 연마한 후 광학현미경을 이용하여 연마된 SiC wafer의 micropipe density와 planar defect density를 측정한 결과, micropipe density는 400개/$ \textrm{cm}^2$이었고 planar defect density는 50개/$\textrm{cm}^2$이었다. 이 6H-SiC wafer와 기판으로 사용된 Acheson 결정의 결정성을 비교하기 위하여 Raman 분광법과 double crystal X-ray diffraction 분석법이 사용되었다. 이 분석에 의해 승화법에 의해 성장된 6H-SiC wafer가 Acheson seed보다 결정성이 우수하였다. Hall effect 측정법에 의해 불순물이 첨가되지 않은 6H-SiC wafer의 전기적인 특성을 측정하였으며 그 결과 캐리어 농도는 $3.91{\times}10^{15}/\textrm {cm}^3$이었고, n-type이었다.

• 한국결정성장학회지
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• 제23권3호
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• pp.142-145
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• 2013

The upconversion (UC) luminescence of $Li^+/Er^{3+}/Yb^{3+}$ co-doped $CaWO_4$ phosphors and effects of $Yb^{3+}$ concentration are investigated in detail. Single crystallized $CaWO_4$ : $Li^+/Er^{3+}/Yb^{3+}$ phosphor can be obtained, co-doped up to 35.0/5.0/30.0 mol% ($Li^+/Er^{3+}/Yb^{3+}$) by solid-state reaction. Under 980 nm excitation, $CaWO_4$ : $Li^+/Er^{3+}/Yb^{3+}$ phosphor exhibited strong green UC emissions visible to the naked eye at 530 and 550 nm induced by the intra 4f transitions of $Er^{3+}$ ($^4H_{11/2}$, $^4S_{3/2}{\rightarrow}^4I_{15/2}$). The optimum doping concentrations of $Yb^{3+}$ that would result in the highest UC luminescence were determined, and a possible UC mechanism that depends on the pumping power is discussed in detail.

• 한국반도체및디스플레이장비학회:학술대회논문집
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• 한국반도체및디스플레이장비학회 2007년도 춘계학술대회
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• pp.179-182
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• 2007

Polycrystaline (poly) 3C-SiC thin film on n-type and p-type Si were deposited by APCVD using HMDS, $H_2$, and Ar gas at $1180^{\circ}C$ for 3 hour. And then the schottky diode with Au/poly 3C-Sic/Si(n-type) structure was fabricated. Its threshold voltage ($V_d$), breakdown voltage, thickness of depletion layer, and doping concentration ($N_D$) value were measured as 0.84 V, over 140 V, 61nm, and $2.7{\times}10^{19}\;cm^3$, respectively. The p-n junction diode fabricated by poly 3C-SiC was obtained like characteristics of single 3C-SiC p-n junction diode. Therefore, its poly 3C-SiC thin films are suitable MEMS applications in conjuction with Si fabrication technology.