• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1477-1479
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• 2008

We report the first TTF compounds having columnar LC phase at room temperature. Based on the thermal, structural, and morphological observations, it was concluded that TTF derivative with long alkyl chains has highly ordered oblique columnar LC at room temperature. The new TTF derivatives have excellent oxidative stability which is desirable for a p-type (hole transport) materials.

• Journal of the Korean Ceramic Society
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• v.51 no.3
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• pp.218-223
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• 2014

The domain structures, dielectric properties, and phase transformation of (001)-oriented $Pb(Mg_{1/3}Nb_{2/3})O_3-x%PbTiO_3$ (PMN-x%PT) crystals for x=20, 30, 35, and 40 mole% have been investigated. PMN-20%PT consists of polar nano-domains (PND) which do not self-assemble into macro-domain plates. PMN-30%PT consists of PNDs which begin to self-assemble into colonies along preferred {110} planes. PMN-35PT consists of miniature polar domains on the nm scale. PMN-40%PT consists of {001} oriented lamella domains on the mm scale that have internal nano-scale heterogeneities. The dielectric properties of poled (001) PMN-x%PT single crystals have been measured for orientations both parallel and perpendicular to the [001] poling direction. The results of the temperature dependence of the dielectric constant and mesh scans for the 30%PT sample demonstrate that the initial monoclinic phase changes to single domain tetragonal phase and to cubic phase with increasing temperature.

• Korean Journal of Materials Research
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• v.19 no.6
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• pp.300-304
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• 2009

The domain structures of annealed (001)-oriented $Pb(Mg_{1/3}Nb_{2/3})O_3-x%PbTiO_3$ (PMN-x%PT) crystals for x = 10, 20, 30, 35, and 40 at% were investigated by Polarized Optical Microscopy (POM) and Scanning Force Microscopy (SFM) in the piezoresponse mode. Both Polar Nano-Domains (PND) and long strip-like domains were clearly observed. The results also showed how the domain structure changed between phases with an increasing x in the PMN-x%PT crystals and the domain hierarchy on various length scales ranging from 40 nm to 0.1 mm. Distorted pseudo-cubic phase (x < 20%) consisted of PNDs that did not self-assemble into macro-domain plates. The rhombohedral phase (x = 30%) consisted of PNDs that began to self-assemble into colonies along preferred {110} planes. The monoclinic phase (x = 35%) consisted of miniature polar domains on the nm scale, whereas, the tetragonal phase (x = 40%) consisted of {001} oriented lamella domains on the mm scale that had internal nano-scale heterogeneities, which self-assembled into macro-domain plates oriented along {001} the mm scale.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.939-942
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• 2000

Single point diamond turning technique for optical crystals is reported in this paper. The main factors influencing the machined surface quality are discovered and regularities of machining process are drawn. Optical crystals have found more and more important applications in the field of modern optics. Optical crystals are mostly brittle materials of poor machinability. The traditional machining method is polishing which has many shortcomings such as low production efficiency, poor ability to be automatically controlled and edge effect of the workpiece. The purpose of our research is to find the optimum machining conditions for ductile cutting of optical crystals and apply the SPDT technique to the manufacturing of ultra precision optical components of brittle material.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1223-1227
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• 2010

In this study, the orientational behavior of thermotropic liquid crystals (LC) supported on a film of protein receptors was examined. Avidin was roller printed and covalently immobilized onto the surface of gold using NHS/EDC chemistry. The orientation of nematic 4-cyano-4'-pentylbiphenyl (5CB) was found to be parallel to the plane of the printed avidin surface before incubation with a solution of biotin. However, protein-receptor complexation induced a random orientation of 5CB, where protein-receptor complexes disturbed the nanoscale topography of the printed protein surface. Atomic force microscopy and ellipsometry was used to confirm printing and the specific interaction of proteins. These results demonstrate that the combination of LC and roller printing can be used to detect specific interactions between biomolecules by manipulating the orientational behavior of LC to the printed protein surfaces.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.463-463
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• 2013

This paper reports the synthesis and characterization of ZnO:Ga nano-structures deposited on Au/SiNx/Si(001) by radio-frequency sputtering. The effect of the temperature on the microstructure of the as-grown ZnO:Ga thin films was examined. The growth mode of ZnO:Ga nano-structures can be explained by the profile coating, i.e. the ZnO nano-structures were formed with a morphological replica of Au seeds. Initially, the ZnO:Ga nano-structures were overgrown on top of Au nano-crystals. Small ZnO:Ga nano-dots were then nucleated on hexagonal ZnO:Ga discs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.469-470
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• 2008

We have studied electro-optic characteristics as a function of splay elastic constants ($K_{11}$) in the fringe-field switching (FFS) mode using the LC with positive dielectric anisotropy. When $K_{11}$ is increased from 7.7pN to 11.7pN, a maximum transmittance is slightly increased and rising time become a little bit fast. However, operating voltage and threshold voltage is independent. In opposition to rising time, decay time is not affected by $K_{11}$. We already know that $K_{11}$ affects tilt angle of liquid crystals. Therefore, on the occasion of high $K_{11}$, liquid crystals are mainly affected by twist deformation because the higher $K_{11}$, the less tilt angle. In the FFS device, high $K_{11}$ is favorable to reduce tilt angle in on state and thus improve rising response time.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.128-129
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• 2005

In this research, non-volatile memory effects and nano-crystal creation have been investigated in SiNx containing Si nano-crystals (Si-nc) produced by ICP-CVD and rapid thermal annealing. The quantum dots were created during rapid thermal annealing of Si-rich SiNx thin films. The quantum dot creation was analyzed with photoluminescence spectra, and in case of Si-rich SiNx, it is conformed that the quantum dots are formed easily at 750$\sim$800nm wavelength.

• Journal of the Korean Ceramic Society
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• v.55 no.2
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• pp.108-115
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• 2018

The increasing demands for three-dimensional (3D) electronic and optoelectronic devices have triggered interest in epitaxial growth of 3D semiconductor materials. However, most of the epitaxially-grown nano- and micro-structures available so far are limited to certain forms of crystal arrays, and the level of control is still very low. In this review, we describe our latest progress in 3D epitaxy of oxide and nitride semiconductor crystals. This paper covers issues ranging from (i) low-temperature solution-phase synthesis of a well-regulated array of ZnO single crystals to (ii) systematic control of the axial and lateral growth rate correlated to the diameter and interspacing of nanocrystals, as well as the concentration of additional ion additives. In addition, the critical aspects in the heteroepitaxial growth of GaN and InGaN multilayers on these ZnO nanocrystal templates are discussed to address its application to a 3D light emitting diode array.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1527-1530
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• 2009

A LCoS micro-display using polymer dispersed liquid crystals (PDLCs) for light switching layer was fabricated. The Si backplane of SVGA ($800{\times}600$) with a pixel size of $14{\times}14mm^2$ was prepared by a $0.35{\mu}m$ 18V CMOS process. PDLCs were filled in the gap between backplane and ITO glass by conventional vacuum filling method. The prepared panels were driven by a field sequential color (FSC) scheme at the frequency of 180Hz and were successful in modulating LED lights to show projection images. The preparation and performance of PDLC-LCoS are presented.