• Korean Journal of Metals and Materials
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• v.49 no.4
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• pp.342-347
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• 2011

We fabricated the silicon nanodots using the low pressure chemical vapor deposition technique to investigate their electron field emission characteristics. Atomic force microscope measurements performed for the silicon nanodot samples having various process parameters, such as, deposition time and deposition pressure, revealed that the silicon nanodots with an average size of 20 nm, height of 5 nm, and density of $1.3\;{\times}\;10^{11}\;cm^{-2}$ were easily formed. Electron field emission measurements were performed with the silicon nanodot layer as the cathode electrode. The current-voltage curves revealed that the threshold electric field was as low as $8.3\;V/{\mu}m$ and the field enhancement factor reached as large as 698, which is compatible with the silicon cathode tips fabricated by other techniques. These electron field emission results point to the possibility of using a silicon-based light source for display devices.

• Journal of Magnetics
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• v.13 no.2
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• pp.70-75
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• 2008

In this study, a MOKE (Magneto-optical Kerr effect) measurement method for magnetic nanostructures is proposed. Theoretically, the MOKE signal enhancement can be predicted and confirmed when an anti-reflection coated substrate is used. Since MOKE is a ratio of reflectivity and the difference between the reflectivities for two magnetic states, when the reflectivity of the substrate part is reduced by employing an anti-reflection coated substrate, MOKE signal enhancement can be achieved. The enhancement is confirmed by simple numerical MOKE calculations. When the reflectivity of an anti-reflection coated substrate is 0.7%, the calculated MOKE signal is about 79% of its bulk values for the 100-nm wide Fe nanowire with a 1500-nm radius laser beam. It was found that, for various numerical calculations, a larger MOKE signal is obtained relative to a smaller substrate reflectivity.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.34-35
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• 2002

CoCrPt alloy films are attracting wide attention for applications to high-density magnetic recording media and hard magnetic layer in spin valve structure due to their high coercivity and strong magnetocrystalline anisotropy. Diblock copolymer templates are one of the most promising candidates for nanoscale patterning otherwise inaccessible by lithographic procedures [1]. In this study, we have investigated magnetic properties of Co$\sub$68/Cr$\sub$18/Pt$\sub$14/ nanodot arrays made by self-assembling polystyrene-block-methyl methacrylate ((PS-b-PMMA), (Mn = 82.5 Kg/mol, with a 1.12 polydispersity)) diblock copolymer. (omitted)

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.1
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• pp.12-19
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• 2006

Metalorganic chemical vapor deposition (MOCYD) techniques have been applied to fabricate semiconducting ZnO thin films and nanostructures, which are promising for novel optoelectronic device applications using their unique multifunctional properties. The growth and characterization of ZnO thin films on Si and $SiO_2$ substrates by MOCYD as fundamental study to realize ZnO nanostructures was carried out. The precise control of initial nucleation processes was found to be a key issue for realizing high quality epitaxial layers on the substrates. In addition, fabrication and characterization of ZnO nanodots with low-dimensional characteristics have been investigated to establish nanostructure blocks for ZnO-based nanoscale device application. Systematic realization of self- and artificially-controlled ZnO nanodots on $SiO_2/Si$ substrates was proposed and successfully demonstrated utilizing MOCYD in addition with a focused ion beam technique.

• Journal of Magnetics
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• v.14 no.1
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• pp.31-35
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• 2009

Herein, the Magneto-Optical Kerr Effect (MOKE) signal enhancement in nanostructures in investigated. It is well known that the MOKE signals of ferromagnetic thin films are enhanced with an additional dielectric layer due to multiple reflections. The MOKE signal is modulated with the additional dielectric layer thickness and is at a maximum when reflectivity is at a minimum. This is not always true in the nanostructures due to the contribution from the non-magnetic substrate portion, especially when substrate reflectivity is minimized and the dependence of the additional dielectric layer thickness for the nanostructure is changed in the case of the continuous thin film. We showed that the MOKE signal for nanostructures could be enhanced with a properly designed, dielectric layer in addition to the anti-reflection coated substrates.

• Proceedings of the Korean Magnestics Society Conference
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• 2014.11a
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• pp.34-34
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• 2014

• Journal of Magnetics
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• v.12 no.1
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• pp.17-20
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• 2007

We performed magnetic force microscopy (MFM) observation on array of Co dots in order to understand magnetic state and magnetization behavior of submicron sized Co dots patterned on GaMnAs bridge. MFM observations showed the magnetization reversal and processes of local magnetization of individual ferromagnetic Co nanodots. Magnetic state of Co dots either single domain or vortex is dependent on geometrical size and thickness. Transition from single domain to vortex state can be realized with MFM tip assisted local field. Magnetization reversal process takes place through sequential reversal of individual dots. Localized inhomogeneous magnetic field can be manipulated by controlling magnetic state of individual Co dot in the array structure.

• Applied Chemistry for Engineering
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• v.33 no.2
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• pp.173-178
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• 2022

A lateral flow immunoassay (LFIA) method using carbon nanodot@silica as a signaling material was developed for analyzing the concentration of retinol-binding protein 4 (RBP4), one of the lung cancer biomarkers. Instead of antibodies mainly used as bioreceptors in nitrocellulose membranes in LFIA for protein detection, aptamers that are more economical, easy to store for a long time, and have strong affinities toward specific target proteins were used. A 5' terminal of biotin-modified aptamer specific to RBP4 was first reacted with neutravidin followed by spraying the mixture on the membrane in order to immobilize the aptamer in a porous membrane by the strong binding affinity between biotin and neutravidin. Carbon nanodot@silica nanoparticles with blue fluorescent signal covalently conjugated to the RBP4 antibody, and RBP4 were injected in a lateral flow manner on to the surface bound aptamer to form a sandwich complex. Surfactant concentrations, ionic strength, and additional blocking reagents were added to the running buffer solution to optimize the fluorescent signal off from the sandwich complex which was correlated to the concentration of RBP4. A 10 mM Tris (pH 7.4) running buffer containing 150 mM NaCl and 0.05% Tween-20 with 0.6 M ethanolamine as a blocking agent showed the optimum assay condition for carbon nanodot@silica-based LFIA. The results indicate that an aptamer, more economical and easier to store for a long time can be used as an alternative immobilizing probe for antibody in a LFIA device which can be used as a point-of-care diagnosis kit for lung cancer diseases.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.590-595
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• 2004

The shape and size variations of the nanopatterns produced on a positive photoresist using a near-field scanning optical microscope(NSOM) are investigated with respect to the process variables. A cantilever type nanoprobe having a 100nm aperture at the apex of the pyramidal tip is used with the NSOM and a He-Cd laser at a wavelength of 442nm as the illumination source. Patterning characteristics are examined for different laser beam power at the entrance side of the aperture( $P_{in}$ ), scan speed of the piezo stage(V), repeated scanning over the same pattern, and operation modes of the NSOM(DC and AC modes). The pattern size remained almost the same for equal linear energy density. Pattern size decreased for lower laser beam power and greater scan speed, leading to a minimum pattern width of around 50nm at $P_{in}$ =1.2$\mu$W and V=12$\mu$m/. Direct writing of an arbitrary pattern with a line width of about 150nm was demonstrated to verify the feasibility of this technique for nanomask fabrication. Application on high-density data storage using azopolymer is discussed at the end.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.627-627
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• 2013

Recently, most studies concerning inorganic CdSe/ZnS quantum dot (QD)-polymer hybrid LEDs have been concentrated on the structure with multiple layers [1,2]. The QD LEDs used almost CdSe materials for color reproduction such as blue, green and red from the light source until current. However, since Cd is one of six substances banned by the Restriction on Hazardous Substances (RoHS) directive and classified into a hazardous substance for utilization and commercialization as well as for use in life, it was reported that the use of CdSe is not suitable to fabricate a photoelectronic device. In this work, we demonstrate a novel, simple and facile technique for the synthesis of ZnO-graphene quasi-core.shell quantum dots utilizing graphene nanodot in order to overcome Cd material including RoHS materials. Also, We investigate the optical and structural properties of the quantum dots using a number of techniques. In result, At the applied bias 10 V, the device produced bluish-white color of the maximum brightness 1118 cd/$m^2$ with CIE coordinates (0.31, 0.26) at the bias 10 V.