• Bulletin of the Korean Chemical Society
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• v.28 no.2
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• pp.193-199
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• 2007

Raman and fluorescence spectroscopies were employed to study the coil effects on the intermolecular structure of a rod-coil liquid crystalline (LC) oligomer, the esterification products of ethyl 4-[4'-oxy-4-biphenylcarbonyloxy]- 4'-biphenylcarboxylate with poly(propylene)oxides (PPO) (DP=12) and poly(ethylene oxide)s (PEO) (DP=12). Three different vibrational modes (carbonyl, aromatic C-H, and aromatic C=C) obtained from the Raman experiment at variable temperature indicate that PPO and PEO coils induce the hydrogen bonding in a different manner. Further information about the micro-environment around the mesogenic unit obtained by fluorescence excitation spectra of P12-4 (LC with PPO coil) and 12-4 (LC with PEO coil) suggests that the mesogenic unit of P12-4 is quite different from that of 12-4 in intermolecular structure. This study supports the results obtained only from Raman spectroscopy, providing more accurate information about the intermolecular structural changes of liquid crystalline polymers at a molecular level during the phase transitions.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.323-323
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• 2010

Saw damage of crystalline silicon wafer is unavoidable factor. Usually, alkali treatment for removing the damage has been carried out as the saw damage removal (SDR) process for priming the alkali texture. It usually takes lots of time and energy to remove the sawed damages for solar grade crystalline silicon wafers We implemented two different mixed acidic solution treatments to obtain the improved surface structure of silicon wafer without much sacrifice of the silicon wafer thickness. At the first step, the silicon wafer was dipped into the mixed acidic solution of $HF:HNO_3$=1:2 ration for polished surface and at the second step, it was dipped into the diluted mixed acidic solution of $HF:HNO_3:H_2O$=7:3:10 ratio for porous structure. This double treatment to the silicon wafer brought lower reflectance (25% to 6%) and longer carrier lifetime ($0.15\;{\mu}s$ to $0.39\;{\mu}s$) comparing to the bare poly-crystalline silicon wafer. With optimizing the concentration ratio and the dilution ratio, we can not only effectively substitute the time consuming process of SDR to some extent but also skip plasma enhanced chemical vapor deposition (PECVD) process. Moreover, to conduct alkali texture for pyramidal structure on silicon wafer surface, we can use only nitric acid rich solution of the mixed acidic solution treatment instead of implementing SDR.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.259-259
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• 2015

Single crystalline indium-tin-oxide (ITO) nanowires (NWs) were grown by sputtering method. A thin Ni film of 5 nm was deposited before ITO sputtering. Thermal treatment forms Ni nanoparticles, which act as templates to diffuse Ni into the sputtered ITO layer to grow single crystalline ITO NWs. This Ni diffusion through an ITO NW was investigated by transmission electron microscope to observe the Ni-tip sitting on a single crystalline ITO NW. Meanwhile, a single crystalline ITO structure was found at bottom and body part of a single ITO NW without remaining of Ni atoms. This indicates the Ni atoms diffuse through the oxygen vacancies of ITO structure. Rapid thermal process (RTP) applied to generate an initial stage of a formation of Ni nanoparticles with variation in time periods to demonstrate the existence of an optimum condition to initiate ITO NW growth. Modulation in ITO sputtering condition was applied to verify the ITO NW growth or the ITO film growth. The Ni-assisted grown ITO layer has an improved electrical conductivity while maintaining a similar transmittance value to that of a single ITO layer. Electrically conductive and optically transparent nanowire-coated surface morphology would provide a great opportunity for various photoelectric devices.

• Journal of Magnetics
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• v.12 no.4
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• pp.137-140
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• 2007

We have studied the temperature dependent magnetic properties and crystalline phase transitionn in small amount Fe doped nickel chromite. The Crystalline structure of $NiCr_{1.7}Fe_{0.3}O_4$ is spinel cubic (Fd-3m) structure with a lattice constant $a_0=8.317\AA$ at room temperature. The magnetic $N\acute{e}el$ temperature $(T_N)$ of the Fe doped nickel chromite sample is determined to be 250 K. The $M\ddot{o}ssbauer$ spectra exhibit that there are two magnetic phases with the two different sites for the $Cr^{3+}$ ions. The spectrum at 4.2 K is fitted to two magnetic components of the magnetic hyperfine fields $H_{hf}=496$ and 485 kOe. From the spectrum at 295 K, the electric quadrupole splittings are observed with large values of 0.49 and 0.50 mm/s, respectively. The values of the isomer shifts at all temperature ranges show that the Fe ions are ferric states. We are suggested that the dynamic Jahn-Teller distortion and anisotropic magnetic relaxation effects due to the crystalline phase transition.

• Textile Coloration and Finishing
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• v.4 no.3
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• pp.91-96
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• 1992

The crystalline character of NaOH and KOH-cellulose complex having different tension ratio was studied using X-ray diffraction analysis. Cellulose crystalline lattices in tension alkali treatment cotton were identified by measuring and indexing the 101, 101, and 002 reflections. According as alkali treatment tension ratio increased on, cellulose gave rise to the formation of I rather than cellulose II. It seemed that a part of the fine structure of cellulose increased orientation with antiparaell and parallel chain crystal structure. The high tension ratio alkali treatment cotton resulted in lower dye sorption and in higher breaking strength and crease recovery.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.303-307
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• 2000

The crystal structure of ZnS fabricated by gas-liquid phase reaction was obtained by XRD and refined by RIETAN near R$_{wp}$ factor 10%. The increasement of HCP phase depended on extra H$_2$S gas and the lattice parameter and crystalline size changed by the relative ratio of multiphase. Using ZnS of the different multiphase ratio and crystalline size, sintered ZnS:Cu, Al green phosphor and the CL property resulted optimum luminescence in the range of 91~94% and 150~190$\AA$, respectably, FCC/HCP ratio and crystalline size. As changing of structure ratio, the reason of different luminescence property is now studying. As well as, after XRD pattern of TiO$_2$powder fitted by RIETAN and the structure factor using MEED method simulated about each atom of (002) plane. Additionally, we proposed RIETAN and MEED were the methods of the study of luminescence mechanism for many phosphor materials.s.

• Analytical Science and Technology
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• v.25 no.1
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• pp.3-6
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• 2012

$xZrO_2-(1-x)SiO_2$ glass precursor with relatively high concentration of zirconium propoxide in metal alkoxide solution was obtained by sol-gel method and then heated at various temperature from 500 to $1,100^{\circ}C$ to investigate the effect of the thermal treatment on the crystalline structure of the glass precursor. Based on X-ray diffraction analysis, the crystalline peak was started to develop at temperature higher than $600^{\circ}C$, and the crystalline phase was considerably increased at $850^{\circ}C$ or higher. With increasing the thermal treatment temperature, the characteristic peaks, such as baddelyite, tetragonal-$ZrO_2$ and zircon, was shown at $35^{\circ}$, $50^{\circ}$ and $60^{\circ}$ of $2{\theta}$.

• Journal of the Korean Ceramic Society
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• v.44 no.4 s.299
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• pp.202-207
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• 2007

High-Quality 1-Dimensional InN single crystalline have been grown by Halide Vapor-Phase Epitaxy on the Au catalyst coated Si substrate using the vapor-liquid-solid growth mechanism. We have been grown 1-dimension InN nanowires having controlled the growth conditions for substrate temperature and gases flow rate. The grown InN nanowire of characteristics for morphologies, crystal structure, and element analysis were carried out by SEM, HR-TEM, and EDS respectively. And the defects of InN crystalline were analyzed by indexing of selective area diffraction pattern with attached HR-TEM. We have successfully obtained the defect-free 1-dimensional InN single crystalline nanowire at the atmosphere pressure.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.641-644
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• 2009

We demonstrated a solvent-assisted soft-lithographic patterning method for producing patterned structure and patterned ordering with lyotropic liquid crystalline polymer (LCP) film. Experimental results showed that the liquid crystalline ordering of lyotropic film could be controlled by shearing effects of the fluidic solvent though the patterned mold channels. In this work, two types of lyotropic LCPs were used to investigate the effects of the alkyl chain length of the lyotropic LCP on producing liquid crystalline ordering through the solvent-assisted fluidic patterning.

• Applied Microscopy
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• v.46 no.3
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• pp.160-163
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• 2016

Effect of dealloying condition on the formation of nanoporous structure in melt-spun $Al_{60}Ge_{30}Mn_{10}$ alloy has been investigated in the present study. In as-melt-spun $Al_{60}Ge_{30}Mn_{10}$ alloy spinodal decomposition occurs in the undercooled liquid during cooling, leading to amorphous phase separation. By immersing the as-melt-spun $Al_{60}Ge_{30}Mn_{10}$ alloy in 5 wt% HCl solution, Al-rich amorphous region is leached out, resulting in an interconnected nano-porous $GeO_x$ with an amorphous structure. The dealloying temperature strongly affects the whole dealloying process. At higher dealloying temperature, dissolution kinetics and surface diffusion/agglomeration rate become higher, resulting in the accelerated dealloying kinetics, i.e., larger dealloying depth and coarser pore-ligament structure.