• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.132-132
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• 2008

Silicon carbide (SiC) is an attractive material for high-power, high-temperature, and high-frequency applications. So far, atomic force microscopy (AFM) has been extensively used to study the surface charges, dielectric constants and electrical potential distribution as well as topography in silicon-based device structures, whereas it has rarely been applied to SiC-based structures. In this work, the surface potential and topography distributions SiC with different doping levels were measured at a nanometer-scale resolution using a scanning kelvin probe force microscopy (SKPM) with a non-contact mode AFM. The measured results were calibrated using a Pt-coated tip and a metal defined electrical contacts of Au onto SiC. It is assumed that the atomically resolved surface potential difference does not originate from the intrinsic work function of the materials but reflects the local electron density on the surface. It was found that the work function of the Au deposited on SiC surface was higher than that of original SiC surface. The dependence of the surface potential on the doping levels in SiC, as well as the variation of surface potential with respect to the schottky barrier height has been investigated. The results confirm the concept of the work function and the barrier heights of metal/SiC structures.

• 한국표면공학회지
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• 제50권4호
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• pp.282-288
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• 2017

$Eu^{3+}$- or $Sm^{3+}$-doped $La_2MoO_6$ phosphors were synthesized with different concentrations of activator ions via a solid-state reaction. The X-ray diffraction patterns exhibited that crystalline structures of all the phosphors were tetragonal systems with the dominant peak occurring at (103) plane, irrespective of the concentration and the type of activator ions. The crystallites showed the pebble-like crystalline shapes and the average crystallite size increased with a tendency to agglomerate as the concentration of $Eu^{3+}$ ions increased. The excitation spectra of $Eu^{3+}$-doped $La_2MoO_6$ phosphors contained an intense charge transfer band centered at 331 nm in the range of 250-370 nm and three weak peaks at 381, 394, and 415 nm, respectively, due to the $^7F_0{\rightarrow}^5L_7$, $^7F_0{\rightarrow}^5L_6$, and $^7F_0{\rightarrow}^5D_3$ transitions of $Eu^{3+}$ ions. The emission spectra under excitation at 331 nm exhibited a strong red band centered at 620 nm and two weak bands at 593 and 704 nm. As the concentration of $Eu^{3+}$ increased from 1 to 20 mol%, the intensities of all the emission bands gradually increased. For the $Sm^{3+}$-doped $La_2MoO_6$ phosphors, the emission spectra consisted of an intense emission band at 607 nm arising from the $^4G_{5/2}{\rightarrow}^6H_{7/2}$ transition and three relatively small bands at 565, 648, and 707 nm originating from the $^4G_{5/2}{\rightarrow}^6H_{5/2}$, $^4G_{5/2}{\rightarrow}^6H_{9/2}$, and $^4G_{5/2}{\rightarrow}^6H_{11/2}$ transitions of $Sm^{3+}$, respectively. The intensities of all the emission bands approached maxima when concentration of $Sm^{3+}$ ions was 5 mol%. These results indicate that the optimum concentrations for highly-luminescent red and orange emission are 20 mol% of $Eu^{3+}$ and 5 mol% of $Sm^{3+}$ ions, respectively.

• 공업화학
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• 제7권6호
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• pp.1125-1131
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• 1996

고체전해질형 연료전지의 산소극 재료로서 페롭스카이트 구조를 갖는 $PrMnO_3$에 Ca과 Sr을 도핑시켜 도핑량에 따른 전기전도도, 산소환원과전압 등의 전기화학적 특성과, 전해질인 yttria stabilized zirconia와의 반응성 그리고 열 팽창률 등을 살펴 보았다. 합성된 페롭스카이트 분말은 대략 $2{\sim}5{\mu}m$의 평균입자 크기를 나타내었는데 이때 입자크기 및 비표면적은 도핑량과 무관하였다. Ca이 30mo1% 도핑되었을 때 전기전도도는 $1000^{\circ}C$에서 $266S{\cdot}cm^{-1}$로 가장 높은 값을 나타내었고, 분극을 통해 살펴 본 산소환원특성도 Ca이 30mol% 도핑되었을 때 가장 우수한 특성을 나타내었다. 전극물질과 전해질인 YSZ를 $1200^{\circ}C$에서 100시간 동안 반응시킨 결과 $PrMnO_3$에 Sr을 도핑시켰을 때보다 Ca을 도핑시킨 것이 반응성이 훨씬 약한 결과를 나타내었다. $Pr_{0.7}Ca_{0.3}MnO_3$의 열팽창계수는 $300{\sim}1000^{\circ}C$의 영역에서 $1.19{\times}10^{-5}K^{-1}$로 측정되었고 이 값은 YSZ의 열팽창계수 $1.15{\times}10^{-5}K^{-1}$과 유사한 값이었다.

• 전기전자학회논문지
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• 제19권4호
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• pp.491-499
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• 2015

Silicon Carbide(SiC)는 높은 열전도도와 넓은 밴드갭 에너지로 인해 고온과 고전압 소자로 사용하는데 큰 장점을 가지고 있는 물질이다. SiC를 이용하여 전력반도체소자를 제작할 경우, 소자가 목표 전압을 충분히 견딜 수 있도록 Edge Termination 기법을 적용하여야한다. Edge Termination 기법에는 여러 가지 방안이 제안되어왔는데, SiC 소자에 가장 적합한 기법은 Junction Termination Extension (JTE)이다. 본 논문에서는 각 JTE 구조별 도핑 농도와 Passivation Oxide Charge 변화에 따른 항복전압의 변화를 살펴보았다. 결과적으로 Single Zone JTE (SZ-JTE)는 1D 시뮬레이션 값의 98.24%, Double Zone JTE (DZ-JTE)는 99.02%, Multiple-Floating-Zone JTE (MFZ-JTE)는 98.98%, Space-Modulated JTE (SM-JTE)는 99.22%의 최대 항복전압을 나타내었고, JTE 도핑 농도 변화에 따른 최대 항복전압의 민감도는 MFZ-JTE가 가장 낮은 반면 SZ-JTE가 가장 높았다. 또한 Passivation Oxide 층의 전하로 인해 소자의 항복전압의 변화를 살펴보았는데, 이에 대한 민감도 역시 MFZ-JTE가 가장 낮았으며 SZ-JTE가 가장 높았다. 결과적으로 본 논문에서는, 짧은 JTE 길이에서 높은 도핑 농도를 필요로 하는 MFZ-JTE보다 DZ-JTE와 SM-JTE가 실제 소자 설계에 있어 가장 효과적인 JTE 기법으로 분석되었다.

• Current Photovoltaic Research
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• 제2권1호
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• pp.28-35
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• 2014

High-efficiency in $Cu(In,Ga)Se_2$ (CIGS) solar cells were usually achieved on soda-lime glass substrates due to Na incorporation that reduces deep-level defects. However, this supply of sodium from sodalime glass to CIGS through Mo back electrode could be limited at low deposition temperature. Na content could be more precisely controlled by supplying Na from known amount of an outside source. For the purpose, an $Na_2S$ layer was deposited on Mo electrode prior to CIGS film deposition and supplied to CIGS during CIGS film. With the $Na_2S$ underlayer a more uniform component distribution was possible at $350^{\circ}C$ and efficiency was improved compared to the cell without $Na_2S$ layer. With more precise control of bulk and surface component profile, CIGS film can be deposited at low temperature and could be useful for flexible CIGS solar cells.

• 한국결정성장학회지
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• 제18권6호
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• pp.253-257
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• 2008

본 연구에서는 자외선 영역에서 발광하는 우수한 특성의 적색 형광체를 얻기 위하여 고상 반응법으로 air 분위기에서 $1200^{\circ}C$에서 6시간 동안 열처리하여 $(Y,\;Zn)_2O_3$:$Eu^{3+}$를 Zn 이온의 농도 변화에 따라 실험하였다. $(Y,\;Zn)_2O_3$:$Eu^{3+}$를 XRD에 의해 비교 분석한 결과 주요 peak들이 JCPDS card(No. 41-1105)와 거의 일치하는 것을 확인하였다. 그러나 Zn 이온치 농도가 5 mol% 이상일 때 XRD에서 ZnO의 peak이 관찰되는 것을 확인 하였다. 이로 인하여 Zn 이온의 농도가 5 mol% 이하일 때 불순물 상 없이 $Y_2O_3$ 구조에 잘 고용되는 것을 확인하였다. $(Y,\;Zn)_2O_3$:$Eu^{3+}$의 발광 peak은 여기 흡수 영역인 ${\lambda}ex=254\;nm$를 기준으로 612 nm 영역에서 $Eu^{3+}$ 이온의 $^5D_0{\rightarrow}^7F_2$에 전형적인 에너지 천이에 의해 가장 강한 발광 peak을 나타내는 것을 확인하였으나 Zn 이온의 농도가 10 mo1% 이상일 때 갑자기 발광 peak이 현저히 감소하는 것을 확인하였고 최대의 발광 peak을 가질 때 형광체의 조성은 $(Y_{0.95},\;Zn_{0.05})_2O_3$:$Eu^{3+}_{0.075}$이였고 입자 size는 $0.4{\sim}3{\mu}m$로 확인되었다.

• Journal of Mechanical Science and Technology
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• 제20권1호
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• pp.1-12
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• 2006

This work reviews the effects of catalyst formulation and exhaust gas composition on soot oxidation in CDPF (Catalytic Diesel Particulate Filter). DOC's (Diesel Oxidation Catalysts) have been loaded with Pt catalyst (Pt/$Al_{2}O_3$) for reduction of HC and CO. Recent CDPF's are coated with the Pt catalyst as well as additives like Mo, V, Ce, Co, Fe, La, Au, or Zr for the promotion of soot oxidation. Alkali (K, Na, Cs, Li) doping of metal catalyst tends to increase the activity of the catalysts in soot combustion. Effects of coexistence components are very important in the catalytic reaction of the soot. The soot oxidation rate of a few catalysts are improved by water vapor and NOx in the ambient. There are only a few reports available on the mechanism of the PM (particulate matter) oxidation on the catalysts. The mechanism of PM oxidation in the catalytic systems that meet new emission regulations of diesel engines has yet to be investigated. Future research will focus on catalysts that can not only oxidize PM at low temperature, but also reduce NOx, continuously self-cleaning diesel particulate filters, and selective catalysts for NOx reduction.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.205-207
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• 2008

The new process for hybrid silicon thin film transistor (TFT) using DPSS laser has been developed for realizing both low-temperature poly-Si (LTPS) TFT and a-Si:H TFT on the same substrate as a backplane of active matrix liquid crystal display. LTPS TFTs are integrated on the peripheral area of the panel for gate driver integrated circuit and a-Si:H TFTs are used as a switching device for pixel in the active area. The technology has been developed based on the current a-Si:H TFT fabrication process without introducing ion-doping and activation process and the field effect mobility of $4{\sim}5\;cm^2/V{\cdot}s$ and $0.5\;cm^2/V{\cdot}s$ for each TFT was obtained. The low power consumption, high reliability, and low photosensitivity are realized compared with amorphous silicon gate driver circuit and are demonstrated on the 14.1 inch WXGA+ ($1440{\times}900$) LCD Panel.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.82-82
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• 2008

One-dimensional (1D) nanowires have been received much attention due to their potential for applications in various field. Recently some logic applications fabricated on various nanowires, such as ZnO, CdS, Si, are reported. These logic circuits, which consist of two- or three field effect transistors(FETs), are basic components of computation machine such as central process unit (CPU). FETs fabricated on nanowire generally have surrounded shapes of gate structure, which improve the device performance. Highly integrated circuits can also be achieved by fabricating on nano-scaled nanowires. But the numerical and SPICE simulation about the logic circuitry have never been reported and analyses of detailed parameters related to performance, such as channel doping, gate shapes, souce/drain contact and etc., were strongly needed. In our study, NAND and NOT logic circuits were simulated and characterized using 2- and 3-dimensional numerical simulation (SILVACO ATLAS) and built-in spice module(mixed mode).

• 공업화학
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• 제7권1호
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• pp.9-17
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• 1996

고체전해질형 연료전지용 전해질로 사용되는 8mol% YSZ($Y_2O_3$ stabilized zirconia)의 소결조건을 변화시켜 이온전도도를 측정하였다. 그 결과 소결조건이 $1400^{\circ}C$, 10시간이었을 때 가장 높은 값인 $10^{-1}S.cm^{-1}$를 나타내었다. 또한 산소극재료로서 $La_{1-x}Sr_xMnO_3$($0{\leq}{\times}{\leq}1$)를 고상반응법으로 제조하여 과전압, 전자 전도도, 전해질인 YSZ와의 계면저항등을 살펴보았다. 그 결과 La에 대한 Sr의 치환량이 50mol%일 때 가장 우수한 특성을 나타내었다.