• 한국재료학회지
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• 제9권5호
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• pp.473-477
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• 1999

Xerographic properties of double-layer photoconductor doped with 4-butyl-4'-methoxyazobenzene (BMAB) as charge-carrier transport material were investigated. BMAB can undergo reversible trans-cis isomerization by light with appropriate wavelength. In the results of measured surface voltage properties for photoconductor doped with BMAB, TNF: BMAB(4-wt%) sample with trans form showed the lowest dark decay, the lowest residual voltage, and the highest sensitivity among cis form. The trans isomer of BMAB has ordering orientation because the molecule possesses a rodlike shape, while the cis isomer has random orientation due to its bent shape. Therefore the molecular arrangement of trans form enhanced charge-carrier transport mobility.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.777-779
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• 2002

We report the performance of pentacene-based organic thin film transistors (OTFT) with PMMA (polymethyl methacrylate) as the gate insulator which was spin-coated on the ITO (indium tin oxide) glass substrate which was used as the gate contact. The pentacene thin film was deposited on the PMMA film and then Au source/drain contacts were deposited through shadow mask. The pentacene film shows better molecular ordering on PMMA compared with $SiO_2$ of Si wafer. The devices exhibited the field effect mobility of ${\sim}0.004cm^2$/Vs and on/off current ratio of ${\sim}10^3$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.3-4
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• 2007

Orientational ordering of polar molecules and excess charges at the interface are main origins of surface polarization. For organic electronics, probing and control of these two surface polarization phenomena are key issues. In this presentation, I report a novel electrical measurement that can directly probe orientational dipolar motion in surface monolayers by Maxwell-displacement-current, and also report a novel optical technique that allows carrier motions in organic materials by measuring the optical second harmonic signals activated by the electric field. Then I discuss how the control of dipolar motions and carrier motions are linked to organic electronics applications such as organic field effect transistors.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 춘계학술대회 논문집 디스플레이 광소자 분야
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• pp.164-168
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• 2005

We report high performance poly (3-hexylthiophene) organic field-effect transistors fabricated on a plastic substrate. The polymer active channel layer was directly printed by the rubber stamp printing method with a pre-patterned elastomer stamp. As a result. organic transistors having average field-effect mobility of 0.079 $cm^2/Vs$ and on/off ratio of $10^4{\sim}10^5$ were realized on a plastic substrate. Also, through the investigation of the molecular ordering of rubber-stamp-printed poly (3-hexylthiophene) films using synchrotron grazing-incidence X-ray diffraction measurements, the films were found to have edge-on structure which is favorable in realizing high performance organic transistors.

• 한국세라믹학회지
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• 제40권4호
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• pp.354-359
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• 2003

The microwave dielectric characteristics of (1-x)(Al$\_$$\frac{1}{2}$/Ta$\_$$\frac{1}{2}$/)O$_2$-x(Mg$\_$1/3/Ta$\_$2/3/)O$_2$ (0$\leq$x$\leq$1.0) ceramics were investigated by crystalstructure, variations of ionic polarizability, and microstructures. As x increased, (1-x)(Al$\_$$\frac{1}{2}$/Ta$\_$$\frac{1}{2}$/)O$_2$-x(Mg$\_$1/3/Ta$\_$2/3/)O$_2$ transformed to tetragonal structure. Because the ionic radius of (Mg$\_$1/3/Ta$\_$2/3/)$\^$4+/was slightly bigger than one of (Al$\_$$\frac{1}{2}$/Ta$\_$$\frac{1}{2}$/)$\^$4+/, the cell parameters increased with increase of (Mg$\_$1/3/Ta$\_$2/3/)O$_2$concentration and coincided with prediction of the molecular additivity rule. As x increased, the compositions revealed ordered phase and were of single phase above 60 mol%. The increase of the ordered phase and grain size enhanced the Q and when ordering was completed at x over 0.6, the grain size was major factor for the increase in the a. Though the grain size increased, however, the porosity deteriorated the q. Therefore, the a depended on the order/disorder, the porosity, and the grain size in regular order.

• 공업화학
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• 제18권5호
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• pp.506-510
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• 2007

전기적 특성을 가지는 4,4',4''-tris(N-(1-naphthyl)-N-phenylamino)-triphenylamine (1-TNATA)가 유기발광소자(OLED)에서 전극으로 사용되는 ITO (Indium Tin Oxide)와 홀 수송층(Hole Transport Layer, HTL) 사이에 박막으로 진공증착되었다. 분자배열이 잘 되어진 1-TNATA의 경우 ITO와 홀 수송층 사이의 계면에서 생기는 전하주입장벽을 줄임으로 소자의 안정성과 효율을 높여준다. 본 연구에서의 라만 스펙트라(Raman spectra) 분석 결과, 증착된 1-TNATA 박막의 열처리와 증착하는 동안 전자기장 처리에 의해서 박막이 집적되고 분자배열이 이루어짐을 확인하였다. 열처리를 한 경우 1-TNATA 박막으로의 전류 흐름이 25% 증가하였다. 또한, $110^{\circ}C$에서 열처리한 1-TNATA 박막으로 제조된 다층유기발광소자의 전원 효율과 발광효율이 향상되었다. 열처리한 박막이 전자기장으로 처리한 박막에 비해 높은 효율을 나타내었다.

• 생명과학회지
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• 제27권1호
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• pp.15-22
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• 2017

치아우식의 주원인균인 Streptococcus mutans (S. mutans)는 산 생성 뿐 아니라 산에 대한 탁월한 저항성을 나타낸다. 본 연구에서는 S. mutans가 pH stress에 노출될 때 형질막 유동성, F-ATPase 활성과 발현 및 양성자 투과성 변화와 그 상관관계를 규명하였다. S. mutans로부터 형질막을 분리한 후 1,6-diphenyl-1,3,5-hexatriene을 사용하여 pH stress가 형질막 유동성 변화에 미치는 영향을 측정하였다. pH 4.8과 pH 8.8에서 배양한 S. mutans는 pH 6.8에서 배양한 S. mutans에 비하여 형질막 유동성이 감소되었다. F-ATPase 활성과 발현은 pH 4.8에서 가장 높았고, pH 8.8에서 가장 낮았다. 양성자 투과성은 pH 4.8과 pH 8.8에서 모두 감소되었으며, 특히 pH 4.8에서의 감소가 컸다. F-ATPase 활성만으로 양성자 투과성이 결정된다면 pH 8.8에서 가장 높아야 하나 pH 6.8보다 감소하는 것은 형질막 유동성 감소에 기인된 양성자 세포내 유입 감소와 관련된 것으로 추정한다. 또한 pH 4.8에서 양성자 투과성이 아주 낮은 것은 높은 F-ATPase 활성에 의한 양성자 세포외 유출 증가 뿐 아니라 형질막 유동성 감소에 의한 양성자 세포내 유입 감소에 기인된 것으로 추정한다. 따라서 pH stress에 의한 형질막 유동성 감소는 S. mutans가 세포내 pH 를 유지하는데 중요한 역할을 하는 것으로 생각되며 에탄올을 포함하여 비특이적으로 세포막 유동성을 증가시키는 약물들은 항우식제에 활용될 수 있을 것으로 추정한다.

• 한국광학회지
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• 제13권4호
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• pp.356-362
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• 2002

비선형광학(NLO) 곁가지형 고분자계 N-(4-nitrophenul)-(L)-prolinol-poly (p-phenylene terephthalates)로 제작된 박막의 분자 배향거동을 제2 고조파발생(SHG)의 비선형광응답을 사용하여 연구하였다. 새로운 펄스 corona 배향 방법으로 NLO 발색단과 고분자 줄기를 비중심대칭 구조로 배향시켜 SHG 신호를 발생시켰다. 유리전이온도 70$^{\circ}C$를 중심으로 25$^{\circ}C$에서 80$^{\circ}C$까지 온도영역에서 반복율을 0.5 ㎑에서 10 ㎑까지 변화시키면서 인가한 펄스 고압으로 corona 배향한 결과로 곁가지 발색단과 고분자 주사슬이 스스로 재 정렬하여 형성한 구역구조를 원자간력 현미경(AFM)으로 관측하였다. 펄스 corona 전압 인가로 NLO 발색단 배향도가 증가되고, 동시에 고분자박막의 가시적손상을 획기적으로 줄이면서 SHG 신호가 증대되었으며 배향 후 이완거동도 개선되었다. 이 새로운 펄스 corona 배향 실험으로 NLO 발색단 및 고분자 주사슬이 배향과정에서 비등방으로 재배열하는 현상을 in situ로 입증할 수 있었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권3호
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• pp.105-110
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• 2002

J-aggregates in the mutual mixing LB films of [6Me-DS]$_{1-x}$ [DO]$_{x}$,[DS]$_{1-x}$ [DO]$_{x}$ and [DSe]$_{1-x}$ [DO]$_{x}$ have been studied by optical absorption, fluorescence and surface pressure-area isotherms. In [6Me-DS]$_{1-x}$ [DO]$_{x}$ films, sharp J-band absorption and fluorescence of [6Me-DS] are linearly shifted to the longer wavelength for the replacement of [6Me-DS] by [DO]. According to the x, a smooth shift of the limited area has been cleared. In the [DS]-[DO] system, the J-band is enhanced at 1:1 composition and strong fluorescence is also observed. Also, the presence of phase separation was suggested in the [DSe]-[DO] system, because the absorption spectra were decomposed into [DSe] and [DO] spectra. On the other hand, in the pressure-area isothermal study, reduction in the molecular occupying area of monolayers has been clarified. This could be ascribed to the enhancement of molecular ordering in J-aggregates. These facts are also believed to reflect the most closely packed arrangement of chromophores in the merocyanine dye monolayers. Thus, it was confirmed that the interaction between mixed dye molecules and the CdC1$_2$+KHCO$_3$subphases affected the J-aggregates of the LB films. Also. it is thought that the J-aggregates are formed non-dimensionally in LB films, such as solution synthesized [DX:DO] assemblies on mixing.s on mixing.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.148-151
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• 2003

The spin density of ${\beta}-MnO_2$ structure was theoretically investigated by $DV-X_{\alpha}$ (the discrete variation $X{\alpha}$) method, which is a sort of the first principle molecular orbital method using Hatre-Fock-Slater approximation. The used cluster model was $[Mn_{14}O_{56}]^{-52}$. The ${\beta}-MnO_2$ is a paramagnetic oxide semiconductor material having the energy band gap of 0.18 eV and an 3 loan-pair electrons in the 3d orbital of an cation. This material exhibits spin-only magnetism and has the magnetic ordering temperature of 94 K. Below this temperature its magnetism appears as antiferromagnetism. The calculations of electronic state showed that if the initial spin condition of input parameters changed, the magnetic state changed from paramagnetic to antiferromagnetic. When d orbital of all Mn atoms in cluster had same initial spin state as only up spin, paramagnetic spin density distribution appeared by the calculation. On the other way, d orbital had alternately changed spin state along special direction the resulted spin distribution showed antiferromagnetism.