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Woo, Joo Hyoeng,Jung, Yongju,Kim, Seok American Scientific Publishers 2017 Journal of nanoscience and nanotechnology Vol.17 No.8
<P>Pt-deposited reduced graphene oxide (RGO) was prepared by a facile method with presence of dopamine hydrochloride in Tris-HCl buffer solution. The electrochemical and morphological property of Pt/(polydopamine (PDA) coated RGO) composite was studied by cyclic voltammetry (CV), field emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM) and fourier transform infrared spectroscopy (FT-IR). These results show that Pt/PDA/RGO hybrids exhibited not only excellent electrocatalytic active but also long-term stability for the oxidation of methanol in direct methanol fuel cells. In addition, platinum nanoparticles were deposited on the surface of the modified RGO without aggregation of metal catalyst compared to pure graphene oxide. These findings indicated that synthesized Pt/PDA/RGO could be promising candidate for catalyst electrodes in many different kinds of fuel cells.</P>
Effect of curing temperature on nano-silver paste ink for organic thin-film transistors.
Kim, Minseok,Koo, Jae Bon,Baeg, Kang-Jun,Noh, Yong-Young,Yang, Yong Suk,Jung, Soon-Won,Ju, Byeong-Kwon,You, In-Kyu American Scientific Publishers 2012 Journal of nanoscience and nanotechnology Vol.12 No.4
<P>Silver (Ag) metal electrode having 20 microm channel length was printed by reverse offset printing (ROP) using nano-silver paste ink for the source/drain of organic thin-film transistors (OTFT). Specific resistance and surface roughness of printed Ag electrodes with increasing curing temperature were investigated, and surface morphology and grain growth mechanism were systematically verified using a scanning electron microscope (SEM) and atomic force microscope (AFM) in order to obtain an optimized ROP Ag electrode. The Ag electrode was applied to fabricate top-gate/bottom-contact poly(3-hexylthiophene) OTFT devices, which showed reproducible OTFT characteristics such as the field-effect mobility, threshold voltage, and an on/off-current ratio of -10(-3) cm2/Vs, 0.36 V, and -10(2), respectively.</P>
Improved Thermal Properties of Graphene Oxide-Incorporated Poly(methyl methacrylate) Microspheres
Heo, Semi,Cho, Se Youn,Kim, Do Hyeong,Choi, Youngeun,Park, Hyun Ho,Jin, Hyoung-Joon American Scientific Publishers 2012 Journal of nanoscience and nanotechnology Vol.12 No.7
<P>Graphene, a single layer of carbon atoms in a two-dimensional lattice, has attracted considerable attention owing to its unique physical, chemical and mechanical properties. In particular, because of its excellent thermal properties such as high thermal conductivity and good thermal stability, graphene has been regarded as a one of the promising candidates for the reinforcing fillers on the polymer composites field. In this study, we prepared the poly(methyl methacrylate) (PMMA)/graphene oxide (GO) nanocomposite by a simple solution mixing process, and examined the thermal reinforcing effects of GO on a PMMA matrix. Using thermogravimetric analysis, differential scanning calorimeter, and thermal conductivity meter, we investigated the effects of GO on the thermal properties of PMMA/GO nanocomposites. With 3 wt% of GO loading, the glass transition temperature (Tg) of the PMMA/GO nanocomposite were increased by more than 7 degrees C and the thermal conductivity of which also improved 1.8 times compared to pure PMMA.</P>
Lee, Kyoung-Min,Hong, Wan-Shick American Scientific Publishers 2011 Journal of nanoscience and nanotechnology Vol.11 No.1
<P>Silicon nitride (SiN(x)) films for a gate dielectric layer of thin film transistors were deposited by catalytic chemical vapor deposition at a low temperature (< or = 200 degrees C). A mixture of SiH4, NH3 and H2 was used as a source gas. Metal-insulator-semiconductor (MIS) capacitor structures were fabricated for current-voltage (I-V) and capacitance-voltage (C-V) measurements. The breakdown voltage characteristics of the SiN(x) films were improved by the increase of NH3/SiH4 and H2/SiH4 mixing ratios and substrate temperatures. H2 treatment was attempted to improve the breakdown voltage further. A breakdown voltage as high as 6.6 MV/cm was obtained after H2 annealing at 180 degrees C. The defect states inside the SiN(x) films were analyzed by photoluminescence spectra. Silicon dangling bonds (2.5 eV) and nitrogen dangling bonds (3.1 eV) were observed. These defect states inside the SiN(x) films disappeared after H2 annealing. Flat band voltage shifts were observed in C-V curves, and their magnitudes decreased as the defect states inside the SiN(x) films decreased.</P>
Fluorescence intensity ratio stereoscopic transform.
Yun, Hoyoung,Min, Junggi,Bang, Hyunwoo,Han, Dong-Chul,Lee, Soon-Geul,Lee, Won Gu American Scientific Publishers 2011 Journal of nanoscience and nanotechnology Vol.11 No.7
<P>A novel approach to 3-D information processing of 2-D cell images is presented, called fluorescence intensity ratio stereoscopic transform (FIRST). Here, we describe its basic principle of image processing and show the results for the ratio of total internal reflection fluorescence (TIRF) to fluorescence intensity. A simple, intuitive transform algorithm would help us to easily obtain a clear stereoscopic image from two 2-D cell images with different fluorescence intensity. For this purpose, nonlinear evanescent-field (EF) imaging of cell-membrane surface and its intracellular structures by using on-chip grating coupler is achieved. This method enabled us to obtain cell images with different signal-to-background ratio and resolution under microfluidic environments. Specifically, we manipulated optic pathway to partially illuminate microscale objects within the microfluidic channel. These findings imply this method will enable selectively to detect optical signals of biomolecular interaction within the cell membrane in a controlled manner. Furthermore, we believe this approach will help to develop an optofluidic sensor for individually detecting dynamic behaviors of intracellular molecules in living cells under microfluidic cell culture environments.</P>
Nano-electromechanical switch-CMOS hybrid technology and its applications.
Lee, B H,Hwang, H J,Cho, C H,Lim, S K,Lee, S Y,Hwang, H American Scientific Publishers 2011 Journal of nanoscience and nanotechnology Vol.11 No.1
<P>Si-based CMOS technology is facing a serious challenge in terms of power consumption and variability. The increasing costs associated with physical scaling have motivated a search for alternative approaches. Hybridization of nano-electromechanical (NEM)-switch and Si-based CMOS devices has shown a theoretical feasibility for power management, but a huge technical gap must be bridged before a nanoscale NEM switch can be realized due to insufficient material development and the limited understanding of its reliability characteristics. These authors propose the use of a multilayer graphene as a nanoscale cantilever material for a nanoscale NEM switchwith dimensions comparable to those of the state-of-the-art Si-based CMOS devices. The optimal thickness for the multilayer graphene (about five layers) is suggested based on an analytical model. Multilayer graphene can provide the highest Young's modulus among the known electrode materials and a yielding strength that allows more than 15% bending. Further research on material screening and device integration is needed, however, to realize the promises of the hybridization of NEM-switch and Si-based CMOS devices.</P>
Shin, Hong-Sik,Oh, Se-Kyung,Kang, Min-Ho,Li, Shi-Guang,Lee, Ga-Won,Lee, Hi-Deok American Scientific Publishers 2011 Journal of nanoscience and nanotechnology Vol.11 No.7
<P>In this paper, a novel Ni silicide with Yb interlayer (Yb/Ni/TiN) on a boron cluster (B18H22) implanted source/drain junction is proposed for the first time, and its thermal stability characteristics are analyzed in depth. The proposed Ni-silicide exhibits a wider RTP temperature window for uniform sheet resistance, surface roughness and better thermal stability than the conventional structure (Ni/TiN). In addition, the cross-sectional profile of the proposed Ni-silicide showed less agglomeration despite the high temperature post-silicidation annealing, and it can be said that the proposed structure was little dependence on the temperature post-silicidation annealing. The improvement of Ni silicide properties is analyzed and found to be due to the formation of the rare earth metal--NiSi (YbNi2Si2), whose peaks were confirmed by XRD. The junction leakage current of the p + -n junction with Yb/Ni/TiN and B18H22 implantation is smaller than that with Ni/TiN by almost one order of magnitude as well as improving the thermal stability of ultra shallow junction.</P>