• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.67-70
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• 2009

Printed electronics are emerging technology to realize various microelectronic devices via a cost-effective method. Here we introduce high performance inkjet printed polymer field-effect transistors and application to complementary integrated circuits with p-type and n-type conjugated polymers. The performance of devices highly depends on the selection of dielectrics, printing condition and device architecture. The device optimization and performances of various integrated circuits, e.g., complementary inverters and ring oscillators will be mainly discussed in this talk.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.598-601
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• 1999

There is currently considerable interest in the applications of conjugated polymers, oligomers and small molecules for thin-film electronic devices. Organic materials have potential advantages to be utilized as semiconductors in field effect transistor and light emitting didoes. In this study, Pentacene thin film transistors(TFTs) were fabricated on glass substrate. Aluminum and Gold wei\ulcorner used fur the gate and source/drain electrodes. Silicon dioxde was deposited as a gate insulator by PECVD and patterned by R.I.E. The semiconductor layer of pentacene was thermally evaporated in vaccum at a pressure of about 10$^{-8}$ Torr and a deposition rate 0.3$\AA$/sec. The fabricated devices exhibited the field-effect mobility as large as 0.07cm$^2$/Vs and on/off current ratio larger than 10$^{7}$

• 폴리머
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• 제39권2호
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• pp.225-234
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• 2015

In this study, we proposed to synthesize thermally stable, soluble and conjugated Schiff base polymer (SbP). For this reason, a specific molecule namely 4,4'-thiodiphenol which has sulfur and oxygen bridge in its structure was used to synthesize bi-functional monomers. Bi-functional amino and carbonyl monomers namely 4,4'-[thio-bis(4,1-phenyleneoxy)] dianiline (DIA) and 4,4'-[thiobis(4,1-phenyleneoxy)]dibenzaldehyde (DIB) were prepared from the elimination reaction of 4,4'-thiodiphenol with 4-iodonitrobenzene and 4-iodobenzaldehyde, respectively. The structures of products were confirmed by elemental analysis, FTIR, $^1H$ NMR and $^{13}C$ NMR techniques. The molecular weight distribution parameters of SbP were determined by size exclusion chromatography (SEC). The synthesized SbP was characterized by solubility tests, TG-DTA and DSC. Also, conductivity values of SbP and SbP-iodine complex were determined from their solid conductivity measurements. The conductivity measurements of doped and undoped SbP were carried out by Keithley 2400 electrometer at room temperature and atmospheric pressure, which were calculated via four-point probe technique. When iodine was used as a doping agent, the conductivity of SbP was observed to be increased. Optical band gap ($E_g$) of SbP was also calculated by using UV-Vis spectroscopy. It should be stressed that SbP was a semiconductor which had a potential in electronic and optoelectronic applications, with fairly low band gap. SbP was found to be thermally stable up to $300^{\circ}C$. The char of SbP was observed 29.86% at $1000^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• 제33권9호
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• pp.3061-3070
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• 2012

Novel 2-hexylthieno[3,2-b]thiophene-containing conjugated molecules have been synthesized via a reduction reaction using tin chloride in an acidic medium. They exhibited good solubility in common organic solvents and good self-film and crystal-forming properties. The single-crystalline objects were fabricated by a solvent slow diffusion process and then were employed for fabricating field-effect transistors (FETs) along with thinfilm transistors (TFTs). TFTs made of 5 and 6 exhibited carrier mobility as high as 0.10-0.15 $cm^2V^{-1}s^{-1}$. The single-crystal-based FET made of 6 showed 0.70 $cm^2V^{-1}s^{-1}$ which was relatively higher than that of the 5-based FET (${\mu}=0.23cm^2V^{-1}s^{-1}$). In addition, we fabricated organic photovoltaic (OPV) cells with new 2-hexylthieno [3,2-b]thiophene-containing conjugated molecules and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester ($PC_{61}BM$) without thermal annealing. The ternary system for a bulk heterojunction (BHJ) OPV cell was elaborated using $PC_{61}BM$ and two p-type conjugated molecules such as 5 and 7 for modulating the molecular energy levels. As a result, the OPV cell containing 5, 7, and $PC_{61}BM$ had improved results with an open-circuit voltage of 0.90 V, a short-circuit current density of 2.83 $mA/cm^2$, and a fill factor of 0.31, offering an overall power conversion efficiency (PCE) of 0.78%, which was larger than those of the devices made of only molecule 5 (${\eta}$~0.67%) or 7 (${\eta}$~0.46%) with $PC_{61}BM$ under identical weight compositions.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.432.2-432.2
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• 2016

A new A-D-A type (Acceptor-Donor-Acceptor) conjugated based on pyridine-borane complex (Donor), non-boron fluorine (Donor) and 2,5-bis(alkyl)-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DPP) (Acceptor) were designed and synthesized via Pd-catalyzed Suzuki cross-coupling reaction. The synthesized boron based complex exhibited high electron affinity, which indicates deep HOMO energy levels and good visible absorption led to their use as donors in BHJ (bulk heterojunction) solar cells. Inverted devices were fabricated, reaching open-circuit voltage as high as 0.91eV. To probe structure-property relationship and search for design principle, we have synthesized pyridine-boron based electron donating small molecules. In this study, we report a new synthetic approach, molecular structure, charge carrier mobility and morphology of blended film and their correlation with the photovoltaic J-V characteristics in details.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2000년도 제1회 학술대회 논문집
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• pp.69-70
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• 2000

There are currently considerable interest in the applications of conjugated polymers, oligomers, and small molecules for thin-film electronic devices. Organic materials have potential advantages to be utilized as semiconductors in field-effect transistors and light-emitting diodes. In this study, pentacene thin-film transistors (TFTs) were fabricated on glass substrate. Aluminums were used for gate electrodes. Silicon dioxide was deposited as a gate insulator by PECVD and patterned by reactive ion etching (R.I.E). Gold was used for the electrodes of source and drain. The active semiconductor pentacene layer was thermally evaporated in vacuum at a pressure of about $10^{-8}$ Torr and a deposition rate $0.3{\AA}/s$. The fabricated devices exhibited the field-effect mobility as large as 0.07 $cm^2/V.s$ and on/off current ratio as larger than $10^7$.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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• pp.170-173
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• 2007

Cruciform conjugated molecule, 4(DP3T)-benzene bearing terthiophene moieties has been synthesized through Horner-Emmons Reaction using 5-dodecyl-5"-aldehyde-[2,2';5',2"] terthiophene as dendrons and octaethyl benzene- 1,2,4,5-tetrayltetrakis(methylene)tetraphosphonate as the core unit; this molecule has been fully characterized. The terthiophene-based molecule exhibits good solubility in common organic solvents and good self-film forming property. They are intrinsically crystalline as they exhibit well-defined X-ray diffraction patterns from uniform orientations of molecules. Thus, intermolecular interaction can be enhanced to affect the carrier transport phenomena after annealing at $148^{\circ}C$. The semiconducting property of 4(DP3T)-benzene have been evaluated in organic field-effect transistors. 4(DP3T)-benzene exhibit carrier mobility as high as $(6.6{\pm}0.5)$ ${\times}$ $10^{-6}cm^2V^{-1}s^{-1}$.

• 대한기계학회논문집A
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• 제31권10호
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• pp.986-992
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• 2007

This paper presents the fabrication and characterization of carbon films pyrolyzed with various photoresists for bioMEMS applications. To verify the usefulness of pyrolyzed carbon films as an electrode material in an electrochemical biosensor developed by the authors, interactions between avidin and biotin on the pyrolyzed carbon film were studied via electrochemical impedance spectroscopy based on electrostatic interactions between avidin and negatively-charged ferricyanide. The pyrolyzed carbon films were characterized using a surface profiler, a precision semiconductor parameter analyzer, a nanoindentor, scanning electron microscopy, and atomic force microscopy. Amine conjugated biotin was immobilized on the electrode using EDC/NHS as crosslinkers after $O_2$ plasma treatment to enhance functional groups on the carbon electrode pyrolyzed at $1000^{\circ}C$ with AZ9260. The detection of avidin binding with different concentrations in a range of 0.75 nM to $7.5\;{\mu}M$ to the pyrolyzed carbon electrode modified with biotin was carried out by measuring the electrochemical impedance change. The results show that avidin binds to the biotin on the electrode not by non-specific interaction but by specific interaction, and that EIS successfully detects this binding event. Pyrolyzed carbon films are a promising material for miniaturization, integration, and low-cost fabrication in electrochemical biosensors.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.355-355
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• 2016

There has been an explosive development of nanocrystal (NC) synthesis and application due to their composition-dependent specific properties. Despite the composition, shape, and size of NCs foremost determine their physicochemical properties, the surface state and molecule conjugation also drastically change their characteristics. To make practical use of NCs, it is a prerequisite to understand the NC surface state and the degree to which they have been modified because the reaction occurs on the interface between the NCs and the surrounding medium. We report in here an analysis method to identify conjugated ligands and their binding states on semiconductor nanocrystals based on their molecular information. Surface science techniques, such as time-of-flight secondary-ion mass spectrometry (ToF-SIMS) and FT-IR spectroscopy, are adopted based on the micro-aggregated sampling method. Typical trioctylphosphine oxide-based synthesis methods of CdSe/ZnS quantum dots (QDs) have been criticized because of the peculiar effects of impurities on the synthesis processes. Since the ToF-SIMS technique provides molecular composition evidence on the existence of certain ligands, we were able to clearly identify the n-octylphosphonic acid (OPA) as a surface ligand on CdSe/ZnS QDs. Furthermore, the complementary use of the ToF-SIMS technique with the FT-IR technique could reveals the OPA ligands' binding state as bidentate complexes.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.51.2-51.2
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• 2015

Understanding interfacial phenomena has been one of the main research issues not only in semiconductors but only in life sciences. I have been trying to meet the atomic scale surface and interface analysis challenges from semiconductor industries and furthermore to extend the application scope to biomedical areas. Optical imaing has been most widely and successfully used for biomedical imaging but complementary ion beam imaging techniques based on mass spectrometry and ion scattering can provide more detailed molecular specific and nanoscale information In this presentation, I will review the 27 years history of medium energy ion scattering (MEIS) development at KRISS and DGIST for nanoanalysis. A electrostatic MEIS system constructed at KRISS after the FOM, Netherland design had been successfully applied for the gate oxide analysis and quantitative surface analysis. Recenlty, we developed time-of-flight (TOF) MEIS system, for the first time in the world. With TOF-MEIS, we reported quantitative compositional profiling with single atomic layer resolution for 0.5~3 nm CdSe/ZnS conjugated QDs and ultra shallow junctions and FINFET's of As implanted Si. With this new TOF-MEIS nano analysis technique, details of nano-structured materials could be measured quantitatively. Progresses in TOF-MEIS analysis in various nano & bio technology will be discussed. For last 10 years, I have been trying to develop multimodal nanobio imaging techniques for cardiovascular and brain tissues. Firstly, in atherosclerotic plaque imaging, using, coherent anti-stokes raman scattering (CARS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) multimodal analysis showed that increased cholesterol palmitate may contribute to the formation of a necrotic core by increasing cell death. Secondly, surface plasmon resonance imaging ellipsometry (SPRIE) was developed for cell biointerface imaging of cell adhesion, migration, and infiltration dynamics for HUVEC, CASMC, and T cells. Thirdly, we developed an ambient mass spectrometric imaging system for live cells and tissues. Preliminary results on mouse brain hippocampus and hypotahlamus will be presented. In conclusions, multimodal optical and mass spectrometric imaging privides overall structural and morphological information with complementary molecular specific information, which can be a useful methodology for biomedical studies. Future challenges in optical and mass spectrometric imaging for new biomedical applications will be discussed.