• 한국결정성장학회지
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• 제23권1호
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• pp.20-26
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• 2013

Special attention in the role of convection in vapor crystal growth has been paid since some single crystals under microgravity environments less than 1 $g_0$ exhibits a diffusive-convection mode and much uniformity in front of the crystal regions than a normal gravity acceleration of 1 $g_0$. The total molar fluxes show asymmetrical patterns in interfacial distribution, which indicates the occurrence of either one single or more than one convective cell. As the gravitational level decreases form 1 $g_0$ down to $1.0{\times}10^{-4}\;g_0$, the intensity of convection, indicative of the maximum molar fluxes, is reduced significantly for ${\Delta}T=30K$ and 90 K. The total molar fluxes decay first order exponentially with the partial pressure of component B, PB (Torr) for 20 Torr ${\leq}PB{\leq}$ 300 Torr, and two gravity accelerations of $g_y=1\;g_0$ and 0.1 $g_0$.

• Bulletin of the Korean Chemical Society
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• 제23권11호
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• pp.1527-1530
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• 2002

1,12-diazacyclodocosane-2,11-dione was first isolated from a plant Phyllanthus niruri Linn. Its structure has been determined by means of spectroscopy methods and X-ray crystallography. Two peptide groups in the big ring (lactam) are the main factors influencing intermolecular contacts. The hydrogen-bond interaction of these hydrophilic groups is observed in the crystal structure. Meanwhile, C-H···O hydrogen bonds in molecules contribute to the formation of the whole crystal. These two kinds of hydrogen-bond form six- member rings among molecules. This compound crystallizes in the triclinic space group P-1 with a= 9.588(1) $\AA$, b= $9.850(1)\AA$, c = $11.810(1)\AA$, $\alpha=$ 68.18(1)$^{\circ}C$ , $\beta=$ 84.98(1), $\gamma$ = 86.03(1)$^{\circ}C$ , V = $1030.66(17)\AA3$ , Z = 2. A disorder of five-member carbon chain in the whole ring is observed in the title compound. The bond angle 105.8(4) is determined for a extreme configuration C(14)-C(15)-C(16), and 117.7(10) for another extreme configuration C(14')-C(15')-C(16'). In this crystal, two molecules are tied each other by short intermolecular hydrogen bonds, the oxygen atom being tied by hydrogen bond to nitrogen atom of another two molecules. The NMR and IR spectral data coincides to the structure of the compound.

• Archives of Pharmacal Research
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• 제2권2호
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• pp.99-110
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• 1979

The crystal structure of sulfapyridine, $C_{11}H_{11}N_{3}O_{2}S$, has been determined by X-ray diffraction method. The compound crystallizees in the monoclinic space group C2/c with a = 12, 80(4), b= 11.72(4), $c= 15.36(5){\AA}, {\beta}= 94(3)^{\circ}$and Z = 8. A total of 1133 observed reflections were collected by the Weissenberg method with CuKaradiation. Structure was solved by the heavy atom method and refined by isostropic block-diagonal least-squares method to the R value of 0.14. The nitrogen in the pyridine ring of sulfapyridine is associated with an extra-annular hydrogen. The C (benzene ring) S-N-C (pyridine ring) group adopts the gauche form with a fonformational angle of $71^{\circ}$. The benzene ring are inclined at angle of $84^{\circ}.to the pyridine ring plane. Sulfapyridine shows three different hydrogen bonding in the crystal. They are two N-H...O hydrogen bonds with the distance of 2.90 and 2.98${\AA}$ respectively, and on N-H...N with the distance of 3.06 ${\AA}$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.473-473
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• 2011

In recent years, organic thin film transistors OTFTs based on conductive-conjugated molecules have received significant attention. We report a fabrication of organic single crystal nanowires that made on Si substrates by liquid bridge-mediated nanotransfer molding (LB-nTM) with polyurethane acrylate (PUA) mold. LB-nTM is based on the direct transfer of various materials from a stamp to a substrate via a liquid bridge between them. In liquid bridge-transfer process, the liquid layer serves as an adhesion layer to provide good conformal contact and form covalent bonding between the organic single crystal nanowire and the Si substrate. Pentacene is the most promising organic semiconductors. However pentacene has insolubility in organic solvents so pentacene OTFTs can be achieved with vacuum evaporation system. However 6, 13-bis (triisopropylsilylethynyl) (TIPS) pentacene has high solubility in organic solvent that reported by Anthony et al. Furthermore, the substituted rings in TIPS-pentacene interrupt the herringbone packing, which leads to cofacial ${\pi}-{\pi}$ stacking. The patterned TIPS-Pentacene single crystal nanowires have been investigated by Atomic force microscopy (AFM), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and electrical properties.

• 대한화학회지
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• 제63권1호
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• pp.29-36
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• 2019

A potentially tetradentate Schiff base ligand, 2-((2-((pyridin-2-ylmethylene)amino)ethyl)amino)ethan-1-ol (PMAE), and its cadmium(II) complex, [$Cd(PMAE)I_2$] (1), were prepared and characterized by elemental analysis, FT-IR, Raman, $^1H$ and $^{13}C$ NMR spectroscopies and single-crystal X-ray diffraction. In the crystal structure of 1, the cadmium atom has a slightly distorted square-pyramidal geometry and a $CdN_3I_2$ environment in which the PMAE acts as an $N_3$-donor. In the crystal packing of the complex, the alcohol and amine groups of the coordinated ligands participate in hydrogen bonding with iodide ions and form $R^2{_2}(14)$ and $R^2{_2}(8)$ hydrogen bond motifs, respectively. In addition to the hydrogen bonds, the crystal network is stabilized by ${\pi}-{\pi}$ stacking interactions between pyridine rings. The thermodynamic stability of the isolated ligand and its cadmium complex along with their charge distribution patterns were studied by DFT and NBO analysis.

• Bulletin of the Korean Chemical Society
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• 제14권6호
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• pp.713-717
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• 1993

The crystal structure of the potassium salt of penicillin V has been studied by the X-ray crystallographic methods. Crystal data are as follows; potassium 3,3-dimethyl-7-oxo-6-phenoxyacetoamido-4-thia-1- azabicyclo[3.2.0]-heptane-2${\alpha}$-carboxylate, $K^+{\cdot}C_{16}H_{18}N_2O_5S^-$, $M_r$= 388.5, triclinic, Pl, a= 9.371 (1), b= 12.497 (2), c= 15.313 (2) ${\AA},\;{\alpha}= 93.74\;(2),\;{\beta}=99.32\;(1),\;{\gamma}=90.17\;(1)^{\circ},\;V=1765.7\;(2)\;{\AA}^3$, Z=4, $D_m=1.461\;gcm^{-1},\;{\lambda}(Cu\;K{\alpha})=1.5418\;{\AA},\;{\mu}=40.1\;cm^{-1}$, F(000)=808, T=296 K. The structure was solved by the heavy atom and difference Fourier methods with intensity data measured on an automated four-circle diffractometer. The structure was refined by the full-matrix least-squares method to a final R= 0.081 for 3563 observed $[I_0{\geq}2{\sigam}(I_0)]$ reflections. The four independent molecules assume different overall conformations with systematically different orientations of the phenyl groups although the penam moieties have the same closed conformations. There are intramolecular hydrogen bonds between the exocyclic amide nitrogen and phenoxy oxygen atoms. The penam moiety is conformationally very restricted although the carboxyl and exocyclic amide groups apparently have certain rotational degrees of freedom but the phenyl group is flexible about the ether bond despite the presence of the intramolecular N-H${\cdots}$O hydrogen bond. There are complicated pseudo symmetric relationships in the crystal lattice. The penam moieties are related by pseudo 20.5 screw axes and the phenyl groups by pseudo centers of symmetry. The potassium ions, related by both pseudo symmetries, form an infinite zigzag planar chain parallel to the b axis. Each potassium ion is coordinated to seven oxygen atoms in a severely distorted pentagonal bipyramid configuration, forming the infinite hydrophilic channels which in turn form the molecular stacks. Between these stacks, there are only lipophilic interactions involving the phenyl groups.

• 한국결정성장학회지
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• 제24권6호
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• pp.237-241
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• 2014

본 연구에서는 상용화되는 AlN 웨이퍼(wafer)를 이용하여 molten KOH/NaOH 화학적 습식 에칭(Wet Chemical Etching)에 따른 표면변화 특성 및 최적의 에칭 조건을 조사하였다. AlN 웨이퍼를 $350^{\circ}C$에서 5분간 에칭 시 Al-face, N-face는 서로 다른 관찰되었다. 특히, Al-face는 에치핏의 형상을 파악하여 결함특성을 관찰하였고, 이로부터 결함 밀도를 계산하여 $2{\times}10^6/cm^2{\sim}10^{10}/cm^2$의 결과를 얻었다. N-face의 경우 육각 뿔(hexagonal pyramids) 형태의 격자결함이 형성되었다. 또한 AlN 웨이퍼의 성장 시 배향을 관찰하기 위해 XRD(X-Ray Diffraction, Rigaku, JAPAN)를 이용하여 분석한 결과 육방정 AlN의 C축 방향에 해당되는 (0002) 및 (0004) 면으로 배향된 상태임을 알 수 있었고, DC-XRD(Double Crystal X-ray Diffraction, bruker, Germany)를 이용하여 rocking curve의 위치에 따라 곡률 반경을 측정했을 때 1.6~17 m의 곡률을 가지고 있는 것으로 나타났다.

• 한국재료학회지
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• 제18권6호
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• pp.339-346
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• 2008

Single-crystal $ZnIn_2S_4$ layers were grown on a thoroughly etched semi-insulating GaAs (100) substrate at $450^{\circ}C$ with a hot wall epitaxy (HWE) system by evaporating a $ZnIn_2S_4$ source at $610^{\circ}C$. The crystalline structures of the single-crystal thin films were investigated via the photoluminescence (PL) and Double-crystal X-ray rocking curve (DCRC). The temperature dependence of the energy band gap of the $ZnIn_2S_4$ obtained from the absorption spectra was well described by Varshni's relationship, $E_g(T)=2.9514\;eV-(7.24{\times}10^{-4}\;eV/K)T2/(T＋489K)$. After the as-grown $ZnIn_2S_4$ single-crystal thin films was annealed in Zn-, S-, and In-atmospheres, the origin-of-point defects of the $ZnIn_2S_4$ single-crystal thin films were investigated via the photoluminescence (PL) at 10 K. The native defects of $V_{Zn}$, $V_S$, $Zn_{int}$, and $S_{int}$ obtained from the PL measurements were classified as donor or acceptor types. Additionally, it was concluded that a heat treatment in an S-atmosphere converted $ZnIn_2S_4$ single crystal thin films into optical p-type films. Moreover, it was confirmed that In in $ZnIn_2S_4$/GaAs did not form a native defects, as In in $ZnIn_2S_4$ single-crystal thin films existed in the form of stable bonds.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1997년도 Proceedings of the 12th KACG Technical Meeting and the 4th Korea-Japan EMGS (Electronic Materials Growth Symposium)
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• pp.121-124
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• 1997

Emergence of advanced materials has been realized by the great demands for sophisticated state devices in high technology industry. It is the ear of speedy evolution of science and technology, in particular, materials processing technology, which enables us to synthesize any materials with respect to its purity and its perfection of crystal structure and shape (form) that have, heretofore not been available. The availability of ultra pure, fine raw materials, single crystals and thick/thin film materials has been largely responsible for such startling progresses that have been made in the realization of unforeseen, functional devices for high technology industry. Of the functional devices such as passive as active devices, non-silicon devices are mostly passive. Piezoelectric, electro-optic, magneto-optic devices, etc. are some of the examples. In this paper, magneto-optic materials for Faraday device, which is little known, are reviewed including its processing toward practical applications.

• Bulletin of the Korean Chemical Society
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• 제25권4호
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• pp.466-470
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• 2004

The crystals of the new melaminium salt, i.e. melaminium acetate acetic acid solvate monohydrate, $C_3H_7N_6^+ {\cdot}CH_3COO^- {\cdot}CH_3COOH{\cdot}H_2O$, were obtained by the slow evaporation of an aqueous solution at room temperature. Powder infrared and Raman spectra were measured and interpreted. The vibrational spectra in the region of internal vibrations of ions corroborate structural data recently published by Perpetuo and Janczak.$^1$ Some spectral features of this new crystal are referred to corresponding one for melamine crystal as well as other melamine complexes in crystalline form. Hydrogen-bonded network present in the crystal gives notable vibrational effect.