• Asian Journal of Atmospheric Environment
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• 제9권2호
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• pp.158-164
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• 2015

The estimation of the concentration of hydroxyl radical (OH) in the atmosphere is essential to build atmospheric models and to understand the mechanisms of the reactions involved in OH. Although water vapor is one of the most abundant species in the troposphere, only a few studies have been performed for the reaction of OH and water vapor. Here I demonstrate an ab initio study on the complex forming reation of OH with $H_2O$ in the gas phase performed based on density functional theory to calculate the reaction rate and the energy states of the reactant and the OH-$H_2O$ complex. The structure of the complex, which belongs to the Cs point group, was optimized at global minima. The transition state was not found at the B3LYP and MP2 levels of theory. Rate constants of the forward and the reverse reactions were calculated as $1.1{\times}10^{-16}cm^3\;molecule^{-1}\;s^{-1}$ and $5.3{\times}10^9\;s^{-1}$, respectively. The extremely slow rates of complex forming reaction and the resulting hydrogen atom exchange reaction of OH and $H_2O$, which are consistent with experimentally determined values, imply a negligible possibility of a change in OH reactivity through the title reaction.

• 통합자연과학논문집
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• 제4권4호
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• pp.294-297
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• 2011

Quality of PEDOT electrode thin film vapor phase-polymerized on 3-aminopropyltriethoxysilane (APS) self-assembled monolayer (SAM) is very crucial for making an ohmic contact between electrode and semiconductor layer of an organic transistor. In order to improve the quality of PEDOT film, the quality of APS-SAM laying underneath the film must be in the best condition. In this study, in order to improve the quality of APS-SAM, the monolayer was self-assembled on $SiO_2$ surface by a dip-coating method under strictly controlled relative humidity (< 18%RH). The quality of APS-SAM and PEDOT thin film were investigated with a contact angle analyzer, AFM, FE-SEM, and four-point probe. The investigation showed that a PEDOT film grown on the humidity-controlled SAM is very smooth and compact (sheet resistivity = 20.2 Ohm/sq) while a film grown under the uncontrolled condition is nearly amorphous and contains quite many pores (sheet resistivity = 200 Ohm/sq). Therefore, this study clearly proves that a highly improved quality of APSSAM can offer a highly conductive PEDOT electrode thin film on it.

• Bulletin of the Korean Chemical Society
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• 제29권7호
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• pp.1349-1352
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• 2008

We report a novel patterning method for a homo-polymeric poly(3-hexylthiophene) (P3HT) nanofilm particularly capable of strong adhesion to a $SiO_2$ surface. An oxidized silicon wafer substrate was micro-contact printed with n-octadecyltrichlorosilane (OTS) monolayer, and subsequently its negative pattern was selfassembled with three different amino-functionalized alkylsilanes, (3-aminopropyl)trimethoxysilane (APS), N- (2-aminoethyl)-3-aminopropyltrimethoxy silane (EDAS), and (3-trimethoxysilylpropyl) diethylenetriamine (DETAS). Then, P3HT nanofilms were selectively grown on the aminosilane pre-patterned areas via the vapor phase polymerization method. To evaluate the adhesion, patterning, and the film itself, the PEDOT nanofilms and SAMs were investigated with a $Scotch^{(R)}$ tape test, contact angle analyzer, ATR-FT-IR, and optical and atomic force microscopes. The evaluation showed that the newly developed all bottom-up process can offer a simple and inexpensive patterning method for P3HT nanofilms robustly adhered to an oxidized Si wafer surface by the mediation of $FeCl_3$ and amino-functionalized alkylsilane SAMs.

• Journal of Korean Society for Atmospheric Environment
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• 제14권E호
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• pp.41-58
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• 1998

In this study, a wide range of volatile organic constituents of environmental tobacco smoke (ETS) were determined using an environmental chamber, where ETS is the sole source of target compounds. ETS was generated in an environmental chamber by a number of different cigarettes, including the Kentucky reference cigarette and eight different commercial brands. More than 30 compounds were measured simultaneously for a total of twelve experimental runs. The target compounds are classified into three major classes, i.e. vapor phase ETS markers including 3-ethnylpyridine (3-EP) and nicotine, carbonyl compounds including formaldehyde, and volatile organic compounds (VOCs). The results from the chamber study were used to generate characterized ratios of selected VOCs to 3-EP, a vapor phase ETS marker. Emission factors for VOCs associated with ETS were also estimated. The characteristic ratios appeared to be generally in good agreement with published data obtained by environmental chamber studies similar to this study. This implies that the ratios may be useful for identifying and quantifying the impact of ETS as a source of target compounds in 'real world' indoor environments, which is affected by a complex mixture of multi-sources. The environmental chamber method described here provides a direct and reliable method to compare the ETS generated by different cigarettes. The method can also be applied to the simultaneous determination of many different ETS components.

• Current Photovoltaic Research
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• 제1권1호
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• pp.27-32
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• 2013

We investigated the growth mechanism of amorphous-phase Si thin films in order to improve the film characteristics and circumvent photo-degradation effects by implementation of hot-wire chemical vapor deposition. Amorphous silicon thin films grown in a silane/hydrogen mixture can be decomposed by a resistive heat filament. The structural properties were observed by Raman spectroscopy, FTIR, SEM, and TEM. The electrical properties of the films were measured by photo-conductivity, dark-conductivity, and photo-sensitivity. The contents of Si-H and $Si-H_n$ bonds were measured to be 19.79 and 9.96% respectively, at a hydrogen flow rate of 5.5 sccm, respectively. The thin film has photo-sensitivity of $2.2{\times}10^5$ without a crystalline volume fraction. The catalyst behavior of the hot-wire to decompose the chemical precursors by an electron tunneling effect depends strongly on the hydrogen mixture rate and an amorphous Si thin film is formed from atomic relaxation.

• 대한화학회지
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• 제40권3호
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• pp.167-172
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• 1996

GaN 단결정 박막은 halide vapor phase epitaxy(HVPE)방법을 사용하여 사파이어 기판위에 헤케로에피탁시하게 성장시켰다. 이렇게 제조된 박막은 n형 전동성을 갖는다. 아연(Zn)을 받개 불순물로 도핑시켜 절연형 GaN 박막을 만들었는데 2.64과 2.43eV의 청색영역에서 발광 피크를 가졌다. 본 연구에의해 GaN 박막은 MIS(metal-insulator-semiconductor) 접합구조로 제작이 가능함을 시사하였고, 이종접합형 발광소자 개발에 기초자료가 될 것으로 전망된다.

• 한국세라믹학회지
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• 제50권6호
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• pp.533-538
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• 2013

Silicon carbide (SiC) materials are typical ceramic materials with a wide range of uses due to their high hardness and strength and oxidation resistance. In particular, due to the corrosion resistance of the material against acids and bases including the chemical resistance against ionic gases such as plasma, the application of SiC has been expanded to extreme environments. In the SiC deposition process, where chemical vapor deposition (CVD) technology is used, the reactions between the raw gases containing Si and C sources occur from gas phase to solid phases; thus, the merit of the CVD technology is that it can provide high purity SiC in relatively low temperatures in comparison with other fabrication methods. However, the product yield rarely reaches 50% due to the difficulty in performing uniform and dense deposition. In this study, using a computational fluid dynamics (CFD) simulation, the gas velocity inside the reactor and the concentration change in the gas phase during the SiC CVD manufacturing process are calculated with respect to the gas velocity and rotational speed of the stage where the deposition articles are located.

• 설비공학논문집
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• 제22권9호
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• pp.614-619
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• 2010

Recently, a problem related to the thermal management in portable electronic and telecommunication devices is becoming issued. That is due to the trend of a slimness of the devices, so it is not easy to find the optimal thermal management solution for the devices. From now on, a pressed circular type cooling device has been mainly used, however the cooling device with thin thickness is becoming needed by the inner space constraint of the applications. In the present study, the silicon flat plate type cooling device with the separated vapor and liquid flow path was designed and fabricated. The normal isothermal characteristics created by vapor-liquid phase change was confirmed through the experimental study. The cooling device with 70 mm of total length showed 6.8 W of the heat transfer rate within the range of $4{\sim}5^{\circ}C/W$ of thermal resistance. In the future, it will be possible to develop the commercialized cooling device by revising the fabrication process and enhancing the thermal performance of the silicon and glass cooling device.

• 한국진공학회지
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• 제18권1호
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• pp.44-48
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• 2009

전기로에서 공급하는 열을 통해 주변 반응 기체와 기판이 열적 평형 상태를 이루고 있는 기존의 박막 성장 방식과 달리, 외부에서 주입시킨 공기를 이용하여 기판 홀더를 냉각시켜 기판과 기판 주변 반응 기체 사이에 온도 차이(temperature gradient)를 발생시키고, 그 온도 차이가 변함에 따라 사파이어 r-면 기판 위에 성장된 질화갈륨 나노 구조체의 구조적 특성이 어떻게 바뀌는지에 대한 연구를 수행하였다. 온도 차이의 크기에 따라 다족(multipod) 형태로 자란 나노 막대의 직경과 밀도, 그리고 길이가 변화함을 확인하였다. 또한, 동일한 온도 차이(temperature gradient)가 있더라도 기판 자체의 온도에 따라 나노막대 끝 단면의 모양이 변화됨을 발견하였다.

• 한국전기전자재료학회논문지
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• 제25권11호
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• pp.922-925
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• 2012

Single crystalline Au nanowires were successfully synthesized in a tube-type furnace. The Au nanowires were grown by vapor phase synthesis technique using solid-liquid-solid (SLS) mechanism on substrates of corning glass and Si wafer. Prior to Au nanowire synthesis, Au thin film served as both catalyst and source for Au nanowire was prepared by sputtering process. Average length of the grown Au nanowires was approximately 1 ${\mu}m$ on both the corning glass and Si wafer substrates, while the diameter and the density of which were dependent on the thickness of the Au thin film. To induce a super-saturated states for the Au particle catalyst and Au molecules during the Au nanowire synthesis, thickness of the Au catalyst thin film was fixed to 10 nm or 20 nm. Additionally, synthesis of the Au nanowires was carried out without introducing carrier gas in the tube furnace, and synthesis temperature was varied to investigate the temperature effect on the resulting Au nanowire characteristics.