• 전자공학회논문지A
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• 제30A권1호
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• pp.23-30
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• 1993

Hydrogenation on the top gate and bottom gate Poly-Si TET's was performed by using Nh$_{3}$ plasma and annealing SiN film deposited by PECVD and then the electric characteristics on Poly-Si TET were investigated. As the time of NA$_{3}$ plasma treatment increaes, on/off current ratio gradually increases and the swing value decreases. The trap densities of graim boundaries in Poly-Si decrease very much during the inital 20min of hydrogenation time, and the decreasing scale becomes smaller after 20 min. The electric characteristics of the top gate TFT are better than those of the bottom gate TFT, it is considered due to the defects at the interface between the Poly-Si and the underlayer, SiO$_{2}$. After NH$_{3}$ plasma was treated for 2 hours for the top gate TFT, as the aging time atroon temperature increases on current was not scacely changed and off current decreases more than 1 order. Gate current density recovers to original value after the aging treatment for 8 days and then the electric characteristics are finally improved. It is suggested that the degraded characteristics of gate oxide are improved, from the variations of C-V characteristics with aging time. For the hydrogenation of isothermal and isochronal annealing SiN film deposited by PECVD, the characteristics of Poly-Si TFT are improved with increasing annealing temperature and are not largely changed with increasing annealing time. This results is good in agreement with the hydrogen reduction in Sin film as variations of annealing temperature and time.

• JSTS:Journal of Semiconductor Technology and Science
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• 제6권1호
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• pp.10-15
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• 2006

Various sizes of erbium/platinum silicided n/p-type Schottky barrier metal-oxide-semiconductor field effect transistors (SB-MOSFETs) are manufactured from $20{\mu}m$ to 10nm. The manufactured SB-MOSFETs show excellent DIBL and subthreshold swing characteristics due to the existence of Schottky barrier between source and channel. It is found that the minimization of trap density between silicide and silicon interface and the reduction of the underlap resistance are the key factors for the improvement of short channel characteristics. The manufactured 10 nm n-type SBMOSFET showed $550{\mu}A/um$ saturation current at $V_{GS}-V_T$ = $V_{DS}$ = 2V condition ($T_{ox}$ = 5nm) with excellent short channel characteristics, which is the highest current level compared with reported data.

• 한국초전도ㆍ저온공학회논문지
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• 제17권4호
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• pp.25-29
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• 2015

In 1987, M. K. Wu and Paul Chu discovered $Y_{1.2}Ba_{0.8}CuO_4$ (YBCO) with critical temperature ($T_c$) of 93 K. It has significantly lowered the cost of cooling of a material up to the point where superconductivity set in. Utilizing the cost reduction of attaining superconductivity and the vast amount of research to understand characteristics of high temperature oxide superconducting materials, there has been effort to use a high temperature superconductor as a coated conductor. It is important to characterize the materials precisely for stable performance before commercializing. We used polarized Raman scattering spectroscopy to study structural and stoichiometric information regarding $YBa_2Cu_3O_{7-x}$, $GdYBa_2Cu_3O_{7-x}$, and $GdBa_2Cu_3O_{7-x}$ produced by three leading groups of producing commercial grade high temperature superconductor coated conductors American Superconductor Corporation, Superpower, and SuNAM.

• Journal of Korean Neurosurgical Society
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• 제50권5호
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• pp.403-408
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• 2011

Objective : Contrary to some clinical belief, there were quite a few studies regarding animal models of intracerebral hemorrhage (ICH) $in$ $vivo$ suggesting that prior use of statins may improve outcome after ICH. This study reports the effect of 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG CoA) reductase inhibitor, simvastatin given before experimental ICH. Methods : Fifty-one rats were subjected to collagenase-induced ICH, subdivided in 3 groups according to simvastatin treatment modality, and behavioral tests were done. Hematoma volume, brain water content and hemispheric atrophy were analyzed. Immunohistochemical staining for microglia (OX-42) and endothelial nitric oxide synthase (eNOS) was performed and caspase-3 activity was also measured. Results : Pre-simvastatin therapy decreased inflammatory reaction and perihematomal cell death, but resulted in no significant reduction of brain edema and no eNOS expression in the perihematomal region. Finally, prior use of simvastatin showed less significant improvement of neurological outcome after experimental ICH when compared to post-simvastatin therapy. Conclusion : The present study suggests that statins therapy after ICH improves neurological outcome, but prior use of statins before ICH might provide only histological improvement, providing no significant impact on neurological outcome against ICH.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.424.1-424.1
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• 2014

Vanadium dioxide (VO2) is a strongly correlated oxide exhibiting a first-order metal-insulator transition (MIT) that is accompanied by a structural phase transition from a low temperature monoclinic phase to a high-temperature rutile phase. VO2 has attracted significant attention because of a variety of possible applications based on its ultrafast MIT. Interestingly, the transition nature of VO2 is significantly affected by stress due to doping and/or interaction with a substrate and/or surface tension as well as defects. Accordingly, there have been considerable efforts to understand the influences of such factors on the phase transition and the fundamental mechanisms behind the MIT behavior. Here, we present the influences of oxygen deficiency, hydrogen doping, and substrate-induced stress on MIT phenomena in single-crystalline VO2 nanobeams. Specifically, the work function and the electrical resistance of the VO2 nanobeams change with the compositional variation due to the oxygen-deficiency-related defects. In addition, the VO2 nanobeams during exposure to hydrogen gas exhibit the reduction of transition temperature and the complex phase inhomogenieties arising from both substrate-induced stress and the formation of the hydrogen doping-induced metallic rutile phase.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.232.2-232.2
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• 2014

Since its discovery in 2004, graphene, a sp2-hybridized 2-Dimension carbon material, has drawn enormous attention. A variety of approaches have been attempted, such as epitaxial growth from silicon carbide, chemical reduction of graphene oxide and CVD. Among these approaches, the CVD process takes great attention due to its guarantee of high quality and large scale with high yield on various transition metals. After synthesis of graphene on metal substrate, the subsequent transfer process is needed to transfer graphene onto various target substrates, such as bubbling transfer, renewable epoxy transfer and wet etching transfer. However, those transfer processes are hard to control and inevitably induce defects to graphene film. Especially for wet etching transfer, the metal substrate is totally etched away, which is horrendous resources wasting, time consuming, and unsuitable for industry production. Thus, our group develops one-step process to directly grow graphene on glass substrate in plasma enhanced chemical vapor deposition (PECVD). Copper foil is used as catalyst to enhance the growth of graphene, as well as a temperature shield to provide relatively low temperature to glass substrate. The effect of growth time is reported that longer growth time will provide lower sheet resistance and higher VSG flakes. The VSG with conductivity of $800{\Omega}/sq$ and thickness of 270 nm grown on glass substrate can be obtained under 12 min growing time. The morphology is clearly showed by SEM image and Raman spectra that VSG film is composed of base layer of amorphous carbon and vertically arranged graphene flakes.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.206.1-206.1
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• 2014

최근 전자 장비의 금속 전도성 패턴 제작에 있어서 직접적인 프린트가 가능한 프린팅 기술이 기존의 복잡한 photolithography 를 대체할 기술로 주목 받고 있다. 이와 함께 금속 전도성 패턴 제작에 사용되는 고가의 전도성 물질인 Ag ink 및 paste 를 저가의 Cu ink 및 paste 로 대체하기 위한 연구가 진행되고 있다. 하지만 일반적으로 copper 는 대기 중 에서 쉽게 산화되어 높은 저항을 야기시킨다. 따라서 Cu ink 또는 paste 를 제작할 때 copper nanoparticles 을 유기 용매에 분산하여 inert atmosphere에서 합성하거나 [1] copper ink 또는 paste 를 substrate 에 프린트하여 reduction atmosphere 에서 소성시킨다 [2]. 이번 연구에서 Cu paste 를 유리 기판에 screen printing 하여 혼합가스(질소 95%, 수소 5%)와 질소 가스 분위기에서 소성하여 Cu 전극의 소성 거동과 전기적 특성을 분석하였다. 4-point probe를 통해 소성된 Cu 전극의 저항을 측정하여 전도도를 조사하였으며 Thermal Gravimetric Analysis (TGA), Fourier Transform Infrared(FTIR)를 통해 소성된 Cu 전극의 유기물 분해가 전도도에 미치는 영향을 분석하고 Field Emission Scanning Electron Microscopy (FESEM)과 High Resolution Transmission Electron Microscopy (HRTEM)을 통해 Cu nanoparticles 의 grain growth가 전도도에 미치는 영향을 조사하였다.

• Applied Science and Convergence Technology
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• 제26권5호
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• pp.133-138
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• 2017

We investigated the interface defect engineering and reaction mechanism of reduced transition layer and nitride layer in the active plasma process on 4H-SiC by the plasma reaction with the rapid processing time at the room temperature. Through the combination of experiment and theoretical studies, we clearly observed that advanced active plasma process on 4H-SiC of oxidation and nitridation have improved electrical properties by the stable bond structure and decrease of the interfacial defects. In the plasma oxidation system, we showed that plasma oxide on SiC has enhanced electrical characteristics than the thermally oxidation and suppressed generation of the interface trap density. The decrease of the defect states in transition layer and stress induced leakage current (SILC) clearly showed that plasma process enhances quality of $SiO_2$ by the reduction of transition layer due to the controlled interstitial C atoms. And in another processes, the Plasma Nitridation (PN) system, we investigated the modification in bond structure in the nitride SiC surface by the rapid PN process. We observed that converted N reacted through spontaneous incorporation the SiC sub-surface, resulting in N atoms converted to C-site by the low bond energy. In particular, electrical properties exhibited that the generated trap states was suppressed with the nitrided layer. The results of active plasma oxidation and nitridation system suggest plasma processes on SiC of rapid and low temperature process, compare with the traditional gas annealing process with high temperature and long process time.

• 한국분무공학회지
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• 제24권4호
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• pp.178-184
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• 2019

Diesel engines have the advantages of higher thermal efficiency and lower CO2 emissions than gasoline engines, but have the disadvantages that particulate matter (PM) and nitrogen oxides (NOx) emissions are greater than those of gasoline engines. In particular, nitrogen oxides (NOx) emitted from diesel engines generates secondary ultrafine dust (PM2.5) through photochemical reactions in the atmosphere, which is fatal to humans. In order to reduce nitrogen oxides (NOx), pre-treatment systems such as EGR, post-treatment systems such as LNT and Urea SCR have been actively studied. The Urea SCR consists of an injection device injecting urea agent and a catalytic device for reducing nitrogen oxides (NOx). The nitrogen oxide (NOx) reduction performance varies greatly depending on the urea uniformity in the exhaust pipe. In this study, spray characteristics according to the spray hole structure were confirmed, and the influence of spray uniformity on spray characteristics was studied through engine evaluation.

• 한국표면공학회지
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• 제29권6호
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• pp.735-738
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• 1996

Amorphous nickelphthalocyanine(NiPc) thin films were prepared by vacuum evaporation and their electrochromic behavior and voltammograms were examined in the five kinds of aqueous electrolytes. Amorphous NiPc films were prepared on indium-tin-oxide(ITO) glass substrates cooled to-$120^{\circ}C$ by using liquid nitrogen under a vacuum of $2.4 \times 10^{-4}$. The voltammetric and electrochromic measurements were made using a potential galvanostat. In order to confirm the color change, optical vis-transmission spectra of the NiPc films were measured by a spectrophotometer with various electrode potential applied. The NiPc amorphous thin films exhibited most clearly electrochromism in $KNO_3$ aqueous electrolyte. The specimen films underwent 3 color transitions (from blue to yellow-green, then to red violet, then to dark blue), corresponding to the three peaks on the voltammograms in $KNO_3$ aqueous electrolyte. Blue is color of the as-prepared film. When the potential was swept, charge compensation was attained upon oxidation by injection of anions from the electrolyte and upon reduction by expulsion of anions.