• Macromolecular Research
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• v.15 no.2
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• pp.160-166
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• 2007

Novel multiblock copolymers, based on segmented sulfonated hydrophilic-hydrophobic blocks, were synthesized and investigated for their application as proton exchange membranes. A series of segmented sulfonated poly(arylene ether sulfone)-b-polyimide multiblock copolymers, with various block lengths, were synthesized via the coupling reaction between the terminal amine moieties on the hydrophilic blocks and naphthalene anhydride functionalized hydrophobic blocks. Successful imidization reactions required a mixed solvent system, comprised of NMP and m-cresol, in the presence of catalysts. Proton conductivity measurements revealed that the proton conductivity improved with increasing hydrophilic and hydrophobic block lengths. The morphological structure of the multiblock copolymers was investigated using tapping mode atomic force microscopy (TM-AFM). The AFM images of the copolymers demonstrated well-defined nanophase separated morphologies, with the changes in the block length having a pronounced effect on the phase separated morphologies of the system. The self diffusion coefficient of water, as measured by $^1H$ NMR, provided a better understanding of the transport process. Thus, the block copolymers showed higher values than Nafion, and comparable proton conductivities in liquid water, as well as under partially hydrated conditions at $80^{\circ}C$. The new materials are strong candidates for use in PEM systems.

• Journal of Magnetics
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• v.15 no.1
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• pp.12-16
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• 2010

Combined study of in-situ stress measurements and atomic force microscopy (AFM) revealed drastic stress relaxation in the CoCrPt and PS(styrene)-PVP(vinyl pyridine) polymer hybrid structure that was closely related to the growth structure of the film. We have observed not only no large initial growth stress at the initial stages of film growth but also twice smaller stress in magnitude with opposite sign in the CoCrPt/PS-PVP/Si sample. The microstructural studies using AFM at the various film growth stages revealed that the film growth structure plays an important role in the stress relaxation mechanism of CoCrPt films on a corrugated polymer surface.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1748-1750
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• 2000

There are currently considerable interests 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 we fabricated the devices based on pentacene as active layer. Octadecyltrichlorosilane (OTS) is used as buffer layer between $SiO_2$ and pentacene. Atomic force microscopy (AFM), X-ray diffraction (XRD), and electrical conductivity were used with OTS on $SiO_2$ 10nm which the pentacene layer was thermally evaporated in vacuum at a pressure of about $2.0\times10^{-6}$ Torr. In the result of AFM, the grain length is grown by using OTS for surface treatment. Electrical conductivity is changed from $3.19{\times}10^{-6}$ S/cm to $2.12{\times}10^{-7}$ S/cm. We observed that electrical conductivity is also increased by surface treatment. According to these results, the surface treated devices exhibited the increase to compared no treatment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.363-366
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• 2000

In this study, SrBi$_2$Ta$_2$$O_{9}$ (SBT) thin films were etched at different Cl$_2$gas mixing ratio in Cl$_2$/Ar. The maximum etch rate of SBT was 883 $\AA$/min in Cl$_2$(20%)/Ar(80%). The result indicates that physical sputtering of charged particles is dominant to chemical reaction in etching SBT thin films. To evaluate the changes of morphology and crystallinity on the near surface of etched SBT, atomic force microscopy (AFM) and x-ray diffraction (XRD) were used. The rms values of etched samples in Ar only or Cl$_2$ only plasma were higher than that of as-deposited, Cl$_2$/Ar Plasma. The SBT (105) crystalinity of the etched samples decreased in Af only or Cla only plasma, but maintain constant in ClyAr plasma. This can be illustrated by a decrease of Bi content or nonvolatile etching products (Sr-Cl and Ta-Cl), resulting in the changes of stoichiometry on the etched surface of the SBT thin films. The decrease of Bi content and nonvolatile etch products were revealed by x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS).).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.203-204
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• 2005

PRAM (Phase change Random Access Memory) is one of the most promising candidates for next generation Non-volatile Memories. The Phase change material has been researched in the field of optical data storage media. Among the phase change materials $Ge_2Sb_2Te_5$(GST) is very well known for its high optical contrast in the state of amorphous and crystalline. However, the characteristics required in solid state memory are quite different from optical ones. In this study, the structural properties of GST thin films with composition were investigated for PRAM. The 100-nm thick GeTe and $Sb_2Te_3$ films were deposited on $SiO_2$/Si substrates by RF sputtering system. In order to characterize the crystal structure and morphology of these films, we performed x-ray diffraction (XRD) and atomic force microscopy (AFM).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.394-395
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• 2006

본 연구에서는 Arachidic acid Langmuir-Blodgett (LB) 막의 표면이미지와 전압-전류 특성을 측정하였다. Arachidic acid는 포화지방산으로 ($CH3(CH_2)_{18}$ COOH)의 구조를 가지며, 크기가 $27.5\;{\AA}$으로 $CH_3(CH_2)_{18}$의 소수기와 COOH의 친수기로 구성되어 있어, LB Trough를 사용하여 박막제작과 분자제어가 쉽다. Chloroform을 용매로 하여 2mmol/l의 농도를 조성하여 ${\pi}$-A 등온선을 통해 기체 상태, 액체 상태, 고체 상태를 관찰하였다. LB막의 제작 및 평가에서 막의 안정성은 ${\pi}$-A곡선, AFM (Atomic force microscopy) 등을 통하여 확인 하였다. 또한 LB 막을 Metal/LB막/Metal 구조의 소자로 제작하여 전압-전류 특성을 측정하였다.

• Transactions on Electrical and Electronic Materials
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• v.9 no.5
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• pp.202-205
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• 2008

We have studied the liquid crystal (LC) orientation behavior on the organic hybrid overcoat layer with ion beam irradiation. Excellent LC alignments of the nematic liquid crystal (NLC) on the ion beam irradiated organic hybrid overcoat layers were observed in various intensities above 600 eV. Pretilt angles of the NLC on the organic hybrid overcoat layers for all ion beam energy intensities were observed from 0.2 to 0.5 degrees. Also, we used the atomic force microscopy (AFM) images for measuring the roughness of the organic hybrid overcoat layers with ion beam irradiation before and after. The surface of organic hybrid overcoat layers was leveled off by the ion beam irradiation. Finally, a good LC alignment thermal stability on the organic hybrid overcoat layer with ion beam irradiation can be achieved.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.471-474
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• 2005

This study investigates the nano/microstructure, the aging response, and the mechanical/tribological properties of the eutectic regions in rheoformed A356 alloy-T5 parts using nano/micro-indentation and mechanical scratching, combined with optical microscopy and atomic force microscope (AFM). Most eutectic Si crystals in the A356 alloy showed a modified morphology as fine-fibers. The loading curve for the eutectic region was more irregular than that of the primary Al region due to the presence of various particles of varying strength. The aging responses of the eutectic regions in the rheoformed A356 alloys aged at $150^{\circ}C$ for different times (0, 2, 4, 8, 10, 16, 24, 36, and 72 h) were investigated. Both Victors hardness $(H_v)$ and indentation $(H_{IT})$ test results showed a similar trend of aging curves, and the peak was obtained at the same aging time of 10 h. A remarkable size-dependence of the tests was found.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.143.2-143.2
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• 2013

Nanomechanical and electrical properties of vanadium dioxide (VO2) thin films across thermal-driven phase transition are investigated with ultra-high vacuum atomic force microscopy. VO2 thin films have been deposited on the n-type heavily doped silicon wafer by pulsed laser deposition. X-ray diffraction reveals that it is textured polycrystalline with preferential orientation of (100) and (120) planes in monoclinic phase. As the temperature increases, the friction decreased at the temperature below the transition temperature, and then the friction increased as increasing temperature above the transition temperature. We attribute this observation to the combined effect of the thermal lubricity and electronic contribution in friction. Furthermore, the dependence of nanoscale conductance on the local pressure was indicated at the various temperatures, and the result was discussed in the view of pressure-induced metal-insulator transition.

• Korean Journal of Materials Research
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• v.6 no.4
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• pp.395-400
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• 1996

반도체 소자가 점점 고집적회되고 고성능화되면서 Si 기판 세정 방법은 그 중요성이 더욱 더 커지고 있다. 특히 ULSI급 소자에서는 세정 방법이 소자 생산수율 및 신뢰성에 큰 영향을 끼치고 있다. 본 연구에서는 HF-last 세정에 UV/O3과 SC-1 세정을 삽입하여 그 영향을 관찰하였다. 세정 방법은 HF-last 세정을 기본으로 split 1(piranha+HF), split 2(piranha+UV/O3+HF), split 3(piraha+SC-1+HF), split 4(piranha+(UV/O3+HF) x3회 반복)의 4가지 세정 방법으로 나누어 실험하였다. 세정을 마친 Si 기판은 Total X-Ray Fluorescence Spectroscopy(AFM)을 사용하여 표면거칠기를 측정하였다. 또한 세정류량을 측정하고, Atomic Force Microscopy(AFM)을 사용하여 표면거칠기를 측정하였다. 또한 세정후 250$\AA$의 gate 산화막을 성장시켜 전기적 특성을 측정하였다. UV/O3을 삽입한 split 2와 split 4세정방법이 물리적, 전기적 특성에서 우수한 특성을 나타냈고, SC-1을 삽입한 split 3세정 방법이 표준세정인 split 1세정 방법보다 우수하지 못한 결과를 나타냈다.