• Macromolecular Research
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• v.17 no.2
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• pp.104-109
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• 2009

Solid-state facilitated, olefin transport membranes were prepared by complexation of poly(styrene-b-iso-prene-b-styrene) (SIS) block copolymer and silver salt. Facilitated olefin transport was not observed up to a silver mole fraction of 0.14, representing a threshold concentration, above which transport increased almost linearly with increasing silver salt concentration. This was because firstly the silver ions were selectively coordinated with the C=C bonds of PI blocks up to a silver mole fraction of 0.20, and secondly the coordinative interaction of the silver ions with the aliphatic C=C bond was stronger than that with the aromatic C=C bond, as confirmed by FT-Raman spectroscopy. Small angle X-ray scattering (SAXS) analysis showed that the cylindrical morphology of the neat SIS block copolymer was changed to a disordered structure at low silver concentrations ($0.01{\sim}0.02$). However, at intermediate silver concentrations ($0.15{\sim}0.20$), disordered-ordered structural changes occurred and finally returned to a disordered structure again at higher silver concentrations (>0.33). These results demonstrated that the facilitated olefin transport of SIS/silver salt complex membrancs was significantly affected by their coordinative interactions and nano-structural morphology.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.209-209
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• 2013

그래핀(graphene)의 가장자리(edge)는 결정구조의 배향성에 따라 지그재그(zigzag)와 안락의자(armchair) 형태로 구분되는데, 나노미터 크기의 그래핀의 전자적 성질은 이러한 가장자리의 배향성에 의해 크게 영향을 받는다고 알려져 있다. 단일층 그래핀 가장자리 사이에서 일어나는 산화실리콘($SiO_2$)의 carbothermal reduction은 선택적으로 지그재그 형태의 가장자리를 생성한다고 알려져 있다. 본 연구에서는 라만 분광법과 원자 현미경(atomic force microscopy)을 이용하여 기계적 박리법으로 만들어진 이중층 그래핀에서 일어나는 carbothermal reaction을 연구하였다. 고온 산화 방법으로 이중층 그래핀에 원형 식각공(etch pit)을 만들고 Ar 기체 속에서 700도 열처리를 진행한 후, 원형 식각공이 육각형으로 확장된 것을 관찰하였다. 이것은 이중층 그래핀도 산화실리콘의 carbothermal reduction을 유발한다는 사실을 보여준다. 그러나 이중층 그래핀의 반응속도는 단일층보다 5배 정도 느린 것이 확인되었는데, 이는 이중층 그래핀의 탄소원자와 산화제로 작용하는 산화실리콘 간의 평균 거리가 단일층보다 더 크다는 사실로 설명할 수 있다. 또한 단일층과 이중층 그래핀 모두 1 기압 Ar 분위기에서보다 진공상태에서 반응속도가 현저히 작다는 사실이 관찰되었다. 진공도와 온도에 따른 반응속도로부터 반응 메커니즘 및 활성화 에너지에 대해 고찰하고자 한다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.207-207
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• 2013

기존의 그래핀 성장에 관한 연구는 열화학기상증착법(Chemical vapor deposition; CVD)을 이용한다. 그래핀 성장 제어 요소로는 촉매 기판인 전이 금속[Ru, Ir, Co, Re, Pt, Pd, Ni, Cu], 기판 전처리 과정, 수소/메탄 가스 혼합비, 작업 진공 상태, 기판온도[$800{\sim}1,000^{\circ}C$, 냉각 속도 등으로 보고 되고 있다. 그래핀 성장 원리는 Cu 촉매 기판에 메탄 가스를 $1,000^{\circ}C$ 온도에서 분해해서 탄소를 고용 시킨 후 급랭하는 도중에 석출되는 탄소에 의해 그래핀 시트가 형성되는 것으로 알려져 있다. 기존의 CVD를 열원을 이용할 경우 내부 챔버에 생기는 잠열에 의해 cooling profile의 제어가 용이하지 않다. 본 연구에서는 근적외선(Near Infrared; NIR) 열원을 이용한 CVD로 챔버 내부 잠열을 최소화하고, 냉각 공정을 Natural, Linear, Convex cooling type으로 디자인해서 cooling profile 제어가 그래핀 성장에 미치는 영향을 연구 하였다. 이렇게 성장된 그래핀을 임의의 기판(SiO2, Glass, PET film) 위에 습식방법으로 전이 시킨 후, 전기적 구조적 및 광학적 특성을 면저항(four-point probe), 전계방사 주사전자현미경(Field Emission Scanning Electron Microscope; FE-SEM), 마이크로 라만 분광법(Micro Raman spectroscopy) 및 광학현미경(optical microscope), 투과도(UV/Vis spectrometer)의 측정으로 잠열이 최소화된 NIR-CVD에서 cooling profile에 따른 그래핀 성장을 평가하였다.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1493-1495
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• 1994

Study on the effect of hydrogen flow rate and $CH_4$ concentration in deposition of the diamond thin films by MWPECVD diamond thin films were deposited on Si substrate from $CH_4-H_2-O_2$ system by MWPE CVD, and identified by SEM, XRD and Raman spectroscopy. The flow rate of hydrogen didn't affect the surface morphology and crystallity of diamond thin films, but did slightly affect growth rate. When the concentration of oxygen was fixed at 40%, the growth rate and crystallity of diamond thin films were gradually improved according to increasment of concentration of $CH_4$ but growth rate of the thin films showed peak at 7% and the crystallity showed peak at 6%.

• Journal of Surface Science and Engineering
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• v.36 no.2
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• pp.148-154
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• 2003

Short ($\tau$=40 $mutextrm{s}$) and high-voltage ($U_{sub}$=2~8 kV) negative substrate bias pulses were used to assist pulsed magnetron sputtering DLC films deposition. Space- and time-resolved probe measurements of the plasma characteristics have been performed. It was shown that in case of high-voltage substrate bias spatial non-uniformity of the magnetron discharge plasma density greatly affected DLC deposition process. By Raman spectroscopy it was found that maximum percentage of s $p^3$-bonded carbon atoms (40 ~ 50%) in the coating was attained at energy $E_{c}$ ~700 eV per deposited carbon atom. Despite rather low diamond-like phase content these coatings are characterized by good adhesion due to ion mixing promoted by high acceleration voltage. Short duration of the bias pulses is also important to prevent electric breakdowns of insulating DLC film during its growth.wth.

• Current Photovoltaic Research
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• v.5 no.4
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• pp.140-144
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• 2017

$CuSbS_2$ (CAS) and $CuSbSe_2$ (CASe) nanocrystals (NCs), which consist of earth-abundant elements, were synthesized by a mechanochemical method. Elemental precursors such as copper, antimony, sulfur, and selenium were used without adding any organic solvents or additives. The NCs were synthesized by milling for a few hours. The sudden phase changes occurred by self-ignition and propagation, as previously observed in other mechanochemical synthetic processes. The XRD, Raman, and TEM analysis were carried out to determine the crystallinity and secondary phase of the as-synthesized CAS and CASe NCs, confirming the phase-pure synthesis of CAS and CASe. Optical properties were investigated by UV-Vis spectroscopy and it was observed that the band gap energies were about 1.1 and 1.5 eV, respectively for CAS and CASe, suggesting the potential for the use as solar cell materials. The NC colloids dispersed in anhydrous ethanol were prepared and coated on Mo substrates by a facile doctor-blade method. The investigation on the solar cell properties of the as-synthesized materials is underway.

• Journal of Microbiology and Biotechnology
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• v.23 no.2
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• pp.274-277
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• 2013

The unique properties of graphene have earned much interest in the fields of materials science and condensedmatter physics in recent years. However, the biological applications of graphene remain largely unexplored. In this study, we investigate the cell culture conditions, which are exposed to graphene onto glass and $SiO_2$/Si using human nerve cell line, SH-SY5Y. Cell viability was 84% when cultured on glass and $SiO_2$/Si coated with graphene as compared to culturing on polystyrene surface. Fluorescence data showed that the presence of graphene did not influence cell morphology. These findings suggest that graphene may be used for biological applications.

• Bulletin of the Korean Chemical Society
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• v.30 no.8
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• pp.1798-1804
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• 2009

In this study, we have studied on improved performance of carbon nanotubes/titanium (CNT/TiO2) structure electrode for methylene blue (MB). The composite electrodes consisting of CNTs and a titanium oxide matrix with phenol resin binder was fabricated with a mixture method. The chemical and morphological structure of CNT/Ti$O_2$ composites were characterized by means of BET surface area, X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis absorption technique, Raman spectroscopy and energy dispersive X-ray (EDX). The electrode showed a remarkably enhanced performance for MB oxidation under UV illumination with or without electro-chemical reaction (ECR). Such a remarkably improved performance of the CNT/Ti$O_2$ structure electrode might be due to the enhanced MB oxidation by electro- and photo-generated electrons and holes in the CNTs and Ti$O_2$ under UV illumination with or without ECR.

• Journal of the Korean Vacuum Society
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• v.7 no.s1
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• pp.160-166
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• 1998

The field emission characteristics of defective diamond films grown by microwave plasma enhanced chemical vapor deposition (MPECVD) have been studied. X-ray diffraction, the poor crystal quality and/or small grain sizes of the diamond phase and the inclusion of the non-diamond carbon phases in these films have been condirmed by raman spectroscopy, scanning electron microscopy, atomic force microscopy, and the reflectance measurements. The degrees of the film defectiveness and the emission characteristics were dependent on the methane concentration. Current-versus-voltage measurements have demonstrated that the defective diamond films have good electron emission characteristics. characteristics strongly suggests the defect-related electron-emission mechanism. The defective diamond films deposited on Si substrates show the field emission current density of 1$\mu\textrm{A}/\textrm{cm}^2$ and 1mA/$\textrm{cm}^2$ have been measured at electric fields as low as 4.5V/$\mu\textrm{m}$ and 7.6V/$\mu\textrm{m}$, respectively. We also observed the similar emission characteristics from the defective diamond film deposited on Cr/Si substrate and could decrease the deposition temperature to $600^{\circ}C$.

• Journal of the Korean Electrochemical Society
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• v.10 no.4
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• pp.262-264
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• 2007

This paper describes a two-step approach for the electrochemical deposition of CdZnS thin films on the polycrystalline Au electrode. Initially, an Au substrate is electrochemically modified with a sulfur layer. In the second step, the layer is electroreduced to $S^{2-}$ in the electrolyte dosed with the requisite amount of $Cd^{2+}$ and $Zn^{2+}$ ions to generate CdZnS films in situ. This approach was validated using a combination of linear sweep voltammetry and electrochemical quartz crystal microgravimetry. Thus synthesized CdZnS thin films have different composition depending on the composition of electrolytes. CdZnS thin films are characterized by energy-dispersive X-ray analysis and Raman spectroscopy.