Kun-Jae Lee

Effect of Complex Agent on Characteristics of Copper Conductive Pattern Formed by Ink-jet Printing

In this study, Cu ion complex ink was successfully synthesized by a modified electrolysis method in which the Cu ions generated from bulk metal plates by an electric field were coordinated with complex agents. The synthesized ink was ink-jet-printed on a flexible substrate and converted to a dense Cu pattern after sintering at 250 °C. The pattern was characterized by X-ray diffractometry, field emission scanning electron microscope, and four-point probe method to confirm the crystal structure, microstructure, and electrical conductivity, respectively. The effect of the type of complex agent on the characteristics of a Cu conductive pattern was also determined using the analysis results. Finally, we conducted the direct writing of conductive dots and lines using the Cu ion complex ink, and confirmed that fine patterning for application in electronics is possible with the Cu ion complex ink.

Investigation of shape controlled silver nanoplates by a solvothermal process

The shape control and growth process of silver nanoplates formed by a solvothermal solution approach was investigated by placing a mixed solution containing silver nitrate, poly(vinyl pyrrolidone) (PVP), N,N-dimethylformamide (DMF) or ethanol in an autoclave and examined the products under various reaction conditions. The formation process in ethanol proceeds slowly taking more than 10h to form a suspension of hexangular single plates, which are no more than 50nm in edge length, while the process in DMF is relatively rapid forming large single plates within 2-4h. These separate nanostructures can be fused extensively toward the edge region to form a larger mass. The different sized plates fused together grew to large films or belts but maintained the same thickness. Apart from the reaction time and temperature, appropriate amounts of PVP and DMF were also found to be critical to the shape control. Relatively small triangular plates with average edge lengths of 20-50nm could be separated easily from the product. UV-vis absorption spectroscopy showed that these nanoplates exhibit a strong absorption band from 470 to 630nm. Compared with other methods, our synthesis is mass-productive, rapid and easily operated. The newly formed silver nanoplates may have many potential applications in the biological, chemical, and electrical industries.

Ultra-long bismuth telluride nanoribbons synthesis by lithographically patterned galvanic displacement

We demonstrated the wafer level batch synthesis and fabrication of single semiconducting thermoelectric nanoribbon based devices by Lithographically Patterned Galvanic Displacement (LPGD). The shape, composition, and dimension of nanoribbons were tailored by adjusting deposition conditions. High resolution TEM images with fast Fourier transform (FFT)-converted selected area electron diffraction (SAED) patterns confirmed the formation of polycrystalline Bi2Te3 intermetallic compound with a rhombohedral structure without elemental Te and Bi. The thickness dependent electrical resistivity of BixTey nanoribbons shows a classic size effect due to the increase in surface boundary scattering. The as-synthesized nanoribbons were n-type semiconductors with no clear trend between field effect carrier mobility and composition, which might be attributed to the trapped charges at the interface between the channel and dielectric layer. The preliminary results on thermoelectric properties (i.e. Seebeck coefficient and power factor) show that the Seebeck coefficient of as-synthesized 0.1 µm thick Bi30Te70 nanoribbon is comparable with bulk counterparts, however, the power factor was lower because of poor crystallinity which leads to higher resistivity.

The influence of polarity of electrodeposited Cu2O thin films on the photoelectrochemical performance

Both polar and non-polar Cu2O thin films were electrodeposited in electrolytes of different pH, and their photoelectrochemical activities in water were analyzed. The surface morphology of these tailored-polarity Cu2O films was analyzed by field emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD), and their photoactivity was characterized through photoluminescence and Mott–Schottky measurement of the defect structure, diffusion length, carrier concentration, and charge separation. Through this, the tetrahedral surface morphology of a polar Cu2O thin film was found to exhibit a higher photocurrent in the visible spectrum than the pyramidal surface morphology of a non-polar Cu2O film. Furthermore, the higher flat-band potential and carrier concentration identified in the polar Cu2O by Mott–Schottky analysis was found to result in a higher charge separation.

Fabrication and Characterization of Ag Nanoparticle Dispersed Polymer Nanofiber and Ag Nanofiber Using Electrospinning Method

Functional nanomaterial is expected to have improved capacities on various fields. Especially, metal nanoparticles dispersed in polymer matrix and metal nanofiber, one of the functional nanomaterials, are able to achieve improvement of property in the electric and other related fields. In this study...

Microstructure and Mechanical Properties of Al 2 O 3 /Fe-Ni Nanocomposite Prepared by Rapid Sintering

A new High Frequency Induction Heating (HFIH) process has been developed to fabricate dense reinforced with Fe-Ni magnetic metal dispersion particles. The process is based on the reduction of metal oxide particles immediately prior to sintering. The synthesized /Fe-Ni nanocomposite powders were formed directly from the selective reduction of metal oxide powders, such as NiO and . Dense /Fe-Ni nanocomposite was fabricated using the HFIH method with an extremely high heating rate of . Phase identification and microstructure of nanocomposite powders and sintered specimens were determined by X-ray diffraction and SEM and TEM, respectively. Vickers hardness experiment were performed to investigate the mechanical properties of the /Fe-Ni nanocomposite.

Development and Application of Metal Nanoparticles for Printed Electronics: Application to Metal Ink in Ink-Jet Technology

최근프린팅기술은 전자부품소재 산업의 대형화 및 저가격화의 해법으로 기대되고 있다. 특히 전자부품소재 프린팅 기술 중 잉크젯공정은 최신 디스플레이용 전극소재, PCB, FPCB 및 기타 소재공정에 이용하려는 움직임이 활발히 진행되고 있다. 그러나 잉크젯 기술은 재료의존도 비중이 높은 기술로서 소재(금속잉크)의 개발이 최우선시 되어야한다. 전자부품소재용 금속잉크에 사용되는 금속 나노입자는 우수한 전기전도성과 산업적응용이 가능해야 한다. 따라서 최근 연구되고 있는 금속 나노입자의 연구결과 중 전자잉크에 적용 가능한 연구결과와 응용분야에 대하여 서술하였다.

Synthesis and electrical properties of (Bi(1/2)Na(1/2))TiO3 (BNT) ferroelectric thin films by liquid sprayed mist chemical vapor deposition technique.

This study aims to synthesize lead-free ferroelectric material, (Bi(1/2)Na(1/2))TiO3 using the Liquid Sprayed Mist Chemical Vapor Deposition (LSMCVD) technique. The mist of precursor solution was vaporized and deposited on two different substrates of Si(100) and (111)Pt/TiO2/SiO2/Si(100) in an oxygen atmosphere. The deposition temperature and time were varied in the range of 400-600 degrees C and 30-90 min. (Bi(1/2)Na(1/2))TiO3 thin film had preferred orientations of (110). The thickness of the thin film deposited was 35-162 nm. The remnant polarization (2Pr) and the dielectric constant were 4.6-16.8 microC/cm2, 325-350, respectively.

Fabrication and Estimation of Au Coated γ-Fe2O3 Nanoparticles for Separation and Purification of Biomolecules

Au coated γ-Fe2O3 nanoparticles were prepared by the changing of surface charge of Au and γ-Fe2O3 nanoparticles with pH. Well Au coated γ-Fe2O3 nanocomposite particles developed in the range between isoelectric point of Au and that of γ-Fe2O3 nanoparticles. Immobilization of glutathione (GSH), crystalline polypeptide containing mercapto group, was successfully performed on the well Au coated γ-Fe2O3 nanocomposite particles. Properties of nanoparticles and GSH immobilized Au/γ-Fe2O3 were characterized by UV-vis, LPA, XRD, and TEM.

Synthesis and Application of Nano Porous La0.6Sr0.4CoO3-δ on an Oxygen Separation Membrane

As the oxygen permeation flux of La0.7Sr0.3Ga0.6Fe0.4O3-δ (LSGF) membranes is lower than commercial membranes, we coated the nano porous La0.6Sr0.4CoO3-δ (LSC) particles to enhance the oxygen permeation flux. The nano porous LSC particles were synthesized in an advanced process to increase the volume fraction of nano pores by ultrasonic spray pyrolysis. The synthesized LSC particles consisted of nano sized primary particles and pores. They also had remarkably high surface area (22 m2/g). It was found that the LSGF membrane coated by the nano porous LSC resulted in significant improvement in the oxygen permeability.