• Korean Journal of Materials Research
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• v.20 no.1
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• pp.25-30
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• 2010

Si nanowire/multiwalled carbon nanotube nanocomposite arrays were synthesized. Vertically aligned Si nanowire arrays were fabricated by Ag nanodendrite-assisted wet chemical etching of n-type wafers using $HF/AgNO_3$ solution. The composite structure was synthesized by formation of a sheath of carbon multilayers on a Si nanowire template surface through a thermal CVD process under various conditions. The results of Raman spectroscopy, scanning electron microscopy, and high resolution transmission electron microcopy demonstrate that the obtained nanocomposite has a Si nanowire core/carbon nanotube shell structure. The remarkable feature of the proposed method is that the vertically aligned Si nanowire was encapsulated with a multiwalled carbon nanotube without metal catalysts, which is important for nanodevice fabrication. It can be expected that the introduction of Si nanowires into multiwalled carbon nanotubes may significantly alter their electronic and mechanical properties, and may even result in some unexpected material properties. The proposed method possesses great potential for fabricating other semiconductor/CNT nanocomposites.

• Macromolecular Research
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• v.12 no.3
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• pp.293-302
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• 2004

We added surface-modified silica nanoparticles to poly(ethylene 2,6-naphthalate) (PEN) to investigate their effect on the mechanical properties on the PEN nanocomposite material. The torque and total torque values of the composites decreased in the silica nanoparticle composites. The tensile modulus of the composites reinforced with unmodified silica nanoparticles increased upon increasing the silica content, while the tensile strength and elongation decreased accordingly. In contrast, stearic acid-modified, silica nanoparticle reinforced PEN composites exhibited an increase in elongation and a decrease in tensile modulus upon addition of the silica nanoparticles because the stearic acid that had adsorbed onto the surface of the silica nanoparticle in multilayers could act as a plasticizer during melt compounding. Stearic acid modification had a small effect on the crystallization behavior of the composites. We calculated theoretical values of the tensile modulus using the Einstein, Kerner, and Nielsen equations and compared these values with the experimental data obtained from the composites. The parameters calculated using the Nielsen equation and the Nicolais- Narkis model revealed that the interfacial adhesion between silica nanoparticles and the PEN matrix could be improved.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1330-1332
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• 2006

In the Langmuir-Blodgett (LB) technique, a monolayer on the water surface is transferred onto a substrate, which is raised and dipped through the surface. From this, multilayers can be obtained in which constituent molecules are periodically arranged. The LB technique has attracted considerable interest in the fabrication of electrical and electronic devices. Many researchers have investigated the electrical properties of monolayer and multiplayer films. Dendrimers represent a new class of synthetic macromolecules characterized by a regularly branched treelike structure. Multiple branching yields a large number of chain ends that distinguish dendrimers from conventional star-like polymers and microgels. The agobenzene dendrimer is one of the dendritic macromolecules that include the azo-group exhibiting a photochromic character. Due to the Presence of the charge transfer element of the azo-group and its rod-shaped structure, these compounds are expected to have potential interest in electronics and ptoelectronics, especially in nonlinear optics. In the present paper, we give pressure stimulation to organic thin films and detect the induced displacement current.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.11
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• pp.977-980
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• 2008

We investigated the effects of power ratio on the electrical and optical properties of Au based Ga-, B- codoped ZnO(GZOB) thin films. GZOB thin films were deposited on Au based poly carbonate(PC) substrate with various power in the range from 60 to 120 W by DC magnetron sputtering. In the result, GZOB films at 100 W exhibited a low resistivity value of $1.12\times10^{-3}\Omega-cm$, and a visible transmission of 80 % with a thickness of 300 nm. This result indicated that the addition of Ga and B in ZnO films leads to the improvement of conductivity and transparent. From the result, we can confirm the possibility of the application as transparent conductive electrodes.

• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.209-211
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• 2004

In the Langmuir-Boldgett(LB) technique, a monolayer on the water surface is transferred on to a substrate, which is raised and dipped through the surface, and one can obtain multilayers in which constituent molecules periodically are arranged in layer. The LB technique has attracted considerable interest in the fabrication of electrical and electronic device, e.g.. Many researchers have investigated the electrical properties of monolayer and multiplayer films. Dendrimers represent a new class of synthetic macromolecules sharacterized by a regularly branched treelike structure. Multiple branching yields a large number of chain ends, which distinguishes dendrimers from conventional starlike polymers and microgels. Azobenzene dendrimer is one of the dendritic macromolecules that includes the azo-group which exhibits a photochromic character. Due to the presence of the charge transfer part, the azo-group, and having a rod-shaped structure, these compounds are expected to have the potential interest in electronics and ptoelectronics, especially in nonlinear optics. In the present paper, we give a pressure stimulation into organic thin films and detect the induced displacement current.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.52-55
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• 2000

Structually organized mono- and multilayers were developed on gold for the catalytic and affinity biosensing using hyper-branched dendrimers. For the catalytic biosensing interface, a new approach to construct a multilayered enzyme film on the electrode surface was developed. The film was prepared by layer-by-layer depositions of dendrimers and periodate-oxidized glucose oxidase. The voltammograms obtained from the GOx/dendrimer multilayered electrodes revealed that bioelectrocatalytic response is directly correlated to the number of deposited bilayers. From the analysis of voltammetric and ellipsometric signals, the coverage of active enzyme per layer during the layering steps was estimated, demonstrating the spatially-ordered multilayer formation. As an extension of the study, dendrimers having various degrees of ferrocenyl modification were prepared and used. The resulting electrodes were electrochemically characterized, and the density of ferrocenyl groups, active enzyme coverage, and sensitivity were estimated. For the affinity-sensing surrface, a biosensor system based on avidin-biotin interaction was developed. As the building block of affinity monolayer, G4 dendrimer having partial ferrocenyl-tethered surface groups was prepared and used. And the biotinylated and electroactive dendritic monolayer was used for the affinity-sensing surface interacting with avidin. Electrochemical characterization of the resulting biosensor was conducted using free enzyme in electrolyte in terms of degree of surface coverage with avidin and subsequent surface shielding.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.144-144
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• 2007

Effects of power ratio on the electrical and optical properties of Au based Ga-, B- codoped ZnO(GZOB) thin films were investigated. GZOB thin films on Au based PC flexible substrate were deposited at various power in the range from 50 to 125 W by DC magnetron sputtering. Au layer was fabricated to achieve good electrical conductivity. The presence of additional boron impurity leads to improve structural defects. Thus, the c-axis orientation along (002) plane was enhanced with the increasing of power ratio and the surface morphology of the films showed a homogeneous and nano-sized microstructure. GZOB films grown at 125W were investigated a low resistivity value of $1{\times}10^{-3}{\Omega}cm$ and a visible transmission of 80% with a thickness of 300nm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.397-397
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• 2007

Multilayer transparent electrodes, having a much lower electrical resistance than the widely used transparent conducting oxide electrodes, were prepared by using radio frequency magnetron sputtering. The multilayer structure consisted of five layers, indium tin oxided(ITO)/zinc oxide(ZnO)/Ag/oxide(ZnO)/ITO. With about 50nm thick ITO films, the multilayer showed a high optical transmittance in the visible range of the spectrum and had color neutrality. The electrical and optical properties of ITO/ZnO/Ag/ZnO/ITO multilayer were changed mainly by Ag film properties, which were affected by the deposition process of the upper layer. Especially ZnO layer was improved to adhesion of Ag and ITO. A high quality transparent electrode, having a resistance as low as and a high optical transmittance of 91% at 550nm, was obtained. It could satisfy the requirement for the flexible OLED and LCD.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.358-359
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• 2006

In the Langmuir-Blodgett (LB) technique, a monolayer on the water surface is transferred onto a substrate, which is raised and dipped through the surface. From this, multilayers can be obtained in which constituent molecules are periodically arranged. The LB technique has attracted considerable interest in the fabrication of electrical and electronic devices. Many researchers have investigated the electrical properties of monolayer and multiplayer films. Dendrimers represent a new class of synthetic macromolecules characterized by a regularly branched treelike structure. Multiple branching yields a large number of chain ends that distinguish dendrimers from conventional star-like polymers and microgels. The azobenzene dendrimer is one of the dendritic macromolecules that include the azo-group exhibiting a photochromic character. Due to the presence of the charge transfer element of the azo-group and its rod-shaped structure, these compounds are expected to have potential interest in electronics and ptoelectronics, especially in nonlinear optics. In the present paper, we give pressure stimulation to organic thin films and detect the induced displacement current.

• Transactions on Electrical and Electronic Materials
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• v.11 no.1
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• pp.1-10
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• 2010

This is an overview paper reporting our most recent work on processing and microstructure of nano-structured oxides and their photoluminescence and photo-catalysis properties. Zinc oxide and related transition metal oxides such as vanadium pentoxide and titanium dioxide were produced by a combination of magnetron sputtering, hydrothermal growth and atmosphere controlled heat treatment. Special morphology and microstructure were created including nanorods arrays, core-brushes, nano-lollipops and multilayers with very large surface area. These structures showed special properties such as much enhanced photoluminescence and chemical reactivity. The photo-catalytic properties have also been promoted significantly. It is believed that two factors contributed to the high reactivity: the large surface area and the interaction between different oxides. The transition metal oxides with different band gaps have much enhanced photoluminescence under laser stimulation. Use of these complex oxide structures as electrodes can also improve the energy conversion efficiency of solar cells. The mixed oxide complex may provide a promising way to high-efficiency photo emitting materials and photo-catalysts.