• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.249-249
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• 2006

We have prepared an amphiphilic wedge-coil molecule consisting of a hydrophobic wedge-like segment and a hydrophilic poly(ethylene oxide) (PEO) segment. The wedge-coil block molecule self-assembles into cylindrical nanofibers in both polar as well as nonpolar solvents. Remarkably, the resulting nanofibers, as solvent polarity change from water to n-hexane, change from highly flexible coil-like to stiff rod-like characteristics. This dynamic switching in the stiffness of the nanofibers in response to solvent polarity is attributed to the structural inversion of cylindrical core from bulky dendritic segments with amorphous nature to crystallizable linear PEO segments.

• Bulletin of the Korean Chemical Society
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• 제24권12호
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• pp.1793-1798
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• 2003

A series of amorphous molecules that possess both photoconductive and electro-optic properties was synthesized in order to investigate photorefractive properties of bifunctional organic-glasses. Diethylaminobenzaldehyde-diphenylhydrazone was covalently attached to 5-(4-diethylamino-benzylidene)-1,3-dimethylpyrimidine-2,4,6-trione through a flexible alkyl chain (3, 4, 5, 6 and 10 carbons) containing two ether linkages. The longer linkage not only lowered the glass transition temperature ($T_g$) of the molecules, but also allowed faster orientation of the chromophore. To examine the photorefractive properties, a 50 ${\mu}$m-thick film was prepared from the mixture of a bifunctional molecule, butyl benzyl phthalate, and $C_{60}$. The photoconductivity of this composite was as high as $8.01\;{\times}\;10^{-12}$ S/cm at 60 V/ ${\mu}$m, and the maximum diffraction efficiency ( ${\eta}_{max}$) of 50 ${\mu}$m-thick film was about 5% at 80 V/ ${\mu}$m.

• 한국정보통신학회논문지
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• 제4권4호
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• pp.809-815
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• 2000

The box capacitor structure with HSG-Si described here reliably achieves a cell capacitance of 28fF with a cell area of a $0.4820\mum^2$ for 128Mbit DRAM. An HSG-Si formation technology with seeding method, which employs Si2H6 molecule irradiation and annealing, was applied for realizing 64Mbit and larger DRAMS. By using this technique, grain size controlled HSG-Si can be fabricated on in-situ phosphorous doped amorphous silicon electrodes. The HSG-Si fabrication technology achieves twice the storage capacitance with high reliability for the stacked capacitors.The box capacitor structure with HSG-Si described here reliably achieves a cell capacitance of 28fF with a cell area of a $0.4820\mum^2$ for 128Mbit DRAM. An HSG-Si formation technology with seeding method, which employs Si2H6 molecule irradiation and annealing, was applied for realizing 64Mbit and larger DRAMS. By using this technique, grain size controlled HSG-Si can be fabricated on in-situ phosphorous doped amorphous silicon electrodes. The HSG-Si fabrication technology achieves twice the storage capacitance with high reliability for the stacked capacitors.

• 한국정보통신학회논문지
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• 제5권6호
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• pp.1128-1135
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• 2001

본 논문에서는 HSG형성을 위한 Si$_2$H$_{6}$의 조사와 어닐링을 통한 seeding method를 64Mbit DRAM에 적용하였다. 이 기술을 사용함으로서 인이 도우핑된 Amorphous 실리콘의 전극에 HSG grain 크기를 조절할 수 있었고, 이 새로운 HSG형성조건은 기존의 stack 캐패시터보다 약 2배의 정전용량을 확보할 수 있었다. 이와같은 방법을 이용한 HSG형성에서 인농도, 저장폴리 증착온도 및 HSG의 두께에 대한 공정 최적 조건으로는 각각 3.0-4.OE19atoms/㎤ , 53$0^{\circ}C$ 및 400$\AA$이었다. 이들 최적화된 공정조건으로 64M bit DRAM 캐패시터에 적용시 질화막의 두께 한계는 65$\AA$으로 확인되었다.

• Journal of Pharmaceutical Investigation
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• 제34권6호
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• pp.443-452
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• 2004

Habit is the description of the outer appearance of a crystal. If the environment of a growing crystal affects its external shape without changing its internal structure, a different habit results. Crystal habit and the internal structure of a drug can affect bulk and physicochemical properties, which range from flowability to chemical stability. A polymorph is a solid crystalline phase of a given compound resulting from the possibility of at least two different arrangements of the molecules of that compound in the solid state. Chemical stability and solubility changes due to polymorphism can have an impact on a drug's bioavailability and its development program. During crystallization from a solution, crystals separating may consist of a pure component or be a molecular compound. Solvates are molecular complexes that have incorporated the crystallizing solvent molecule in their lattice. When the solvent incorporated in the solvate is water, it is called a hydrate. To distinguish solvates from polymorphs, which are not molecular compounds, the term pseudopolymorph is used. Identification of possible hydrate compounds is important since their aqueous solubilities can be significantly less than their anhydrous forms. Conversion of an anhydrous compound to a hydrate within the dosage form may reduce the dissolution rate and extent of drug absorption. An amorphous solid may be treated as a supercooled liquid in which the arrangement of molecules is random. Amorphous solids lack the three-dimensional long-range order found in crystalline solids. Since amorphous forms are usually of higher thermodynamic energy than corresponding crystalline forms, solubilities as well as dissolution rates are generally greater. A study on crystal form includes characterization of (l)crystal habit, (2)polymorphism, (3)pseudopolymorphism, (4)amorphous solid.

• 폴리머
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• 제24권1호
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• pp.128-132
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• 2000

Polycaprolactone (PCL) 블록의 함량이 62.7 wt%인 PCL-폴리아미드 블록공중합체와 poly(vinyl chloride) (PVC)의 상용거동을 시차주사열량계로 열적 성질을 관찰하여 조사하고, 블렌드물의 인장물성을 측정하였다. PCL과 PVC 세그먼트는 상용성을 가졌으며, PVC의 함량이 많은 경우 PCL의 결정화가 방해받아 PCL과 PVC 세그먼트로 구성된 비결정성 균일상이 형성됨을 알 수 있었다. PCL/PVC 균일 비결정상과 폴리아미드의 결정상이 병존하는 경우 균일 비결정상의 유리전이온도와 결정상의 녹는점 사이의 온도 영역에서 블렌드물은 고무탄성을 가졌다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2000년도 추계종합학술대회
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• pp.475-479
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• 2000

The box capacitor structure with H5G-Si described here reliably achieves a cell capacitance of 28fF with a cell area of a 0.482f${\mu}{\textrm}{m}$$^2$ for 128Mbit DRAM. An H5G-Si formation technology with seeding method, which employs Si$_2$H$_{6}$ molecule irradiation and annealing, was applied for realizing 64Mbit and larger DRAMS. By using this technique, grain size controlled H5G-Si can be fabricated on in-situ phosphorous doped amorphous silicon electrodes. The HSG-Si fabrication technology achieves twice the storage capacitance with high reliability for the stacked capacitors.s.

• 한국세라믹학회지
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• 제27권6호
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• pp.707-712
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• 1990

The basic zirconium sulfate was prepared from ZrOCl2.8H2O and H2SO4 in the 9$0^{\circ}C$ aqueous solution. The pH and amount of unreacted zirconium in the solution that reacton had completed was 0.2 and 10%. As the pH was increased to 1.4 by NH4OH theresulting precipitates were the mixtures of the basic zirconium sulfate and the zirconium hydroxide although the precipitates were recovered completely. The thermal decomposition behavior of this sample has been examined by thermal analysis(TG-DTA), X-ray diffraction study, infrared spectroscopy and sulfur analysis. As a result, it was found that the precipitates have perfectly been decomposed at 85$0^{\circ}C$ accompanying to the release of a molecule of water below 25$0^{\circ}C$ and 85% sulfate at about $600^{\circ}C$. The thermally decomlposed products were initially amorphous phase, which were become metastable tetragonal phase with increment of temperature and finally transformed to the stable monoclinic phase at 100$0^{\circ}C$.

• Applied Microscopy
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• 제21권2호
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• pp.67-75
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• 1991

[ $C_{60}$ ] molecule, the Buckminsterfullerene, has generated great interest because of its unique molecular structure and of superconductivity exhibited in its alkali-doped solids. We have investigated the molecular stacking and crystal structure of $C_{60}$ thin crystals formed on amorphous carbon film. The $C_{60}$ powder which was chromatographically purified was dissolved in benzene. The thin crystals of $C_{60}$ were observed with a 300 keV transmission electron microscope. Electron diffraction analysis and direct imaging of its molecular stacking were carried out. It was found from this work that the molecules of $10.0{\AA}$ diameter are arrayed hexagonally on substrate surface and $8.7{\AA}$ lattice planes are quite often found in several types of ED patterns, which can never be explained with a fcc model. Therefore the structure of $C_{60}$ thin crystals is hcp, although we cannot fully exclude the possibility of co-existence of hcp and fcc.

• Current Applied Physics
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• 제18권11호
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• pp.1294-1299
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• 2018

In this paper, we demonstrate the feasibility of constructing DNA nanostructures (i.e. DNA rings and double-crossover (DX) DNA lattices) with appropriate doxorubicin hydrochloride (DOX) concentration and reveal significant characteristics for specific applications, especially in the fields of biophysics, biochemistry and medicine. DOX-intercalated DNA rings and DX DNA lattices are fabricated on a given substrate using the substrateassisted growth method. For both DNA rings and DX DNA lattices, phase transitions from crystalline to amorphous, observed using atomic force microscopy (AFM) occurred above a certain concentration of DOX (at a critical concentration of DOX, $30{\mu}M$ of $[DOX]_C$) at a fixed DNA concentration. Additionally, the coverage percentage of DNA nanostructures on a given substrate is discussed in order to understand the crystal growth mechanism during the course of annealing. Lastly, we address the significance of optical absorption and photoluminescence characteristics for determining the appropriate DOX binding to DNA molecules and the energy transfer between DOX and DNA, respectively. Both measurements provide evidence of DOX doping and $[DOX]_C$ in DNA nanostructures.