Papers by Author: C.J. Kang

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Authors: In-Je Yi, Ju-Ho Kim, C.J. Kang, Jae Hyun Park, Yong Sang Kim
Abstract: The performances of an electrochemical detector (ECD) using Prussian blue (PB) modified indium tin oxide (ITO) electrode were investigated. PB is one of the well-known catalytic materials. PB offers electrocatalytic reaction between electrode and analytes (dopamine and catechol). We optimized the PB film thickness that would catalyze redox reaction efficiently using surface topography from atomic force microscopy (AFM). Capillary electrophoresis (CE) and amperometric method were used to separate and detect the testing analytes. The results showed that the PB film could serve as an excellent mediator, which catalyzes electron transfer. We measured electropherograms for the testing analytes consisting of catechol and dopamine with their concentrations of 100 µM and 10 µM, respectively.
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Authors: Jung Min Kim, Hyun Jung Her, J.H. Yoon, Jae Wan Kim, Y.J. Choi, C.J. Kang, D. Jeon, Yong Sang Kim
Abstract: We investigated the characteristics of pentacene thin films of different materials for gate insulators using atomic force microscope (AFM) and x-ray diffraction (XRD). The pentacene thin films are fabricated by evaporation on different polymer substrates. We used HMDS (Hexa Methyl Di Silazane), PVA (Poly Vinyl Alcohol) and PMMA (Poly Methyl Meth Acrylate) for the polymer substrates, on which pentacene is deposited at various substrate temperatures. The case of pentacene deposited on the PMMA has the largest grain size and least trap concentration. We also fabricated pentacene TFTs with the PMMA gate insulator. Pentacene TFTs with PMMA gate insulator, shows high field-effect mobility (uFET= 0.03 cm2/Vs) and large on/off current ratio (>105) and small threshold voltage (Vth= -6 V).
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Authors: Kyung-Ah Yoo, Kwang Ho Na, Seung-Ryong Joung, D. Jeon, Y.J. Choi, Yong Sang Kim, C.J. Kang
Abstract: We propose an electrical detection method for detecting the various bio-molecules effectively with microcantilevers. The piezoresistive microcantilevers were fabricated employing surface micromachining technique that has attractive advantages in terms of cost efficiency, simplicity, and ability of fabricating in array. The fluid cell system for injection of bio-molecular solution is fabricated using polydimethylsiloxane (PDMS) and a fused silica glass. The microcantilever is deflected with respect to the difference of the surface stress caused by the formation of self-assembled bio-molecules on the gold coated side of the microcantilever. We confirmed that the deflections occurred by the bio-molecule adsorption and microcantilever can be widely used to a &-TAS and a lab-on-a-chip as a sensor for the potential detection of various biomolecules.
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Authors: Jung Min Kim, Hyun Jung Her, Jeong Min Son, Y. Khang, Eun Hye Lee, Yong Sang Kim, Y.J. Choi, C.J. Kang
Abstract: Scanning probe microscope (SPM) with a conducting tip was used to electrically probe silicon nanocrystals (Si NCs) embedded in a SiO2 layer. The Si NCs were generated by the laser ablation method with compressed Si powder followed by a sharpening oxidation. The size of Si NCs is in the range of 10-50 nm, and the density is around 1011 /cm2. Using a conducting tip, the charge was injected directly into each Si NC, and the image contrast change and dC/dV curve shift caused by the trapped charges were monitored. The results were compared with those of the conventional MOS capacitor.
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Authors: Sung Hwak Park, S.H. Kim, J.K. Shin, Jae Wan Kim, C.J. Kang, Yong Sang Kim, Y.J. Choi
Abstract: For the investigation of high aspect ratio structures with Atomic Force Microscope (AFM), the cantilevers with very sharp and long tips are useful. Electron beam induced deposited(EBID) tips can be simply fabricated by aligning the electron beam directly down the vertical axis of Si cantilever and then irradiating a single spot on the cantilever for a proper time in the dominant atmosphere of residual gases generated by the oil of the diffusion pump of the Scanning Electron Microscope (SEM). However, the EBID tips cannot grow over 1&m in the residual gas atmosphere since there is a little carbon source. We could enhance the height of tips by dipping the cantilever into the organic solvents, drying it in the vacuum chamber and irradiating electron beam on it. With this process, we could acquire the tip whose base diameter is 180nm and effective length is 3.18&m. In addition, we observed that the growth behaviors of the tips are different in accordance with the species of the solvents and we will discuss the effects of the organic solvents on the growth of the tips.
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Authors: Hyun Jung Her, Jung Min Kim, Yun Soo Lim, Jae Wan Kim, Y.J. Choi, C.J. Kang, Yong Sang Kim
Abstract: We produced highly uniform nanoporous thin films of the dense array of titania (TiO2) pores of 70~80 nm in diameter with nanoimprinting method. Titania in HCl and 2-propanol solution was coated on an indium tin oxide (ITO) surface and embossed with an array of PMMA nanopoles which was produced using a nanoporous alumina (Al2O3) template. Two-step anodization was introduced to produce highly uniform and dense nanopores on the aluminum surface. The polymethyl methacrylate (PMMA) was poured onto and infiltrated into the nanoporous alumina surface which was heated at 150 oC. The alumina nanopores and aluminum plate were removed by wet-etching leaving an array of PMMA nanopoles. These highly uniform nanostructured titania films will be very useful for photovoltaic and photocatalytic applications where nanostructuring of surface with controlled dimensions are essential.
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Authors: Jong Chul Yoo, C.J. Kang, D. Jeon, Yong Sang Kim
Abstract: We propose a new PDMS microfluidic system including microvalves and a micropump that are easily integrated on the same substrate with the same process steps. The pumping rate of the fabricated microfluidic system was measured under various frequency and duty-ratio of applied power. The maximum pumping rate of about 26 nl/min is measured under the duty ratio of 1 % at 2 Hz of the applied pulse voltage. The dynamic response of the microvalve in the microfluidic system is measured under the on/off alternation with the applied power of 100 mW.
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