• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.237.1-237.1
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• 2016

Electrical properties of graphene-based field effect transistors (G-FETs) can be degraded in ambient conditions owing to physisorbed oxygen or water molecules on the graphene surface. Passivation technique is one of a fascinating strategy for fabrication of G-FETs, which allows to sustain electrical properties of graphene in the long term without disrupting its inherent properties: transparency, flexibility and thinness. Ironically, despite its importance in producing high performance graphene devices, this method has been much less studied compared to patterning or device fabrication processes. Here we report a novel surface passivation method by using atomically thin self-assembled alkane layers such as C18- NH2, C18-Br and C36 to prevent unintentional doping effects that can suppress the degradation of electrical properties. In each passivated device, we observe a shift in charge neutral point to near zero gate voltage and it maintains the device performance for 1 year. In addition, the fabricated PG-FETs on a plastic substrate with ion-gel gate dielectrics exhibit not only mechanical flexibility but also long-term stability in ambient conditions. Therefore, we believe that these highly transparent and ultra-thin passivation layers can become a promising candidate in a wide range of graphene based electronic applications.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.11 s.254
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• pp.1425-1432
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• 2006

Coating layers on a coated sheet steel frequently affect distributions of strain rate of sheets and deteriorate the frictional characteristics between sheets and tools in sheet metal forming. Thus, it is important to identify the deformation behavior of these coatings to ensure the success of the sheet forming operation. In this study, the technique using nano-indentation test, FE-simulation and Artificial Neural Network(ANN) were proposed to determine the power law stress-strain behavior of coating layer and the power law behavior of extracted coating layers was examined using FE-simulation of drawing and nano-indentation process. Also, deep drawing test was performed to estimate the formability and frictional characteristic of coated sheet, which was calculated using the linear relationship between drawing force and blank holding force obtained from the deep drawing test. FE-simulations of the drawing process were respectively carried out for single-behavior FE-model having one stress-strain behavior and for layer-behavior FE-model which consist of coating and substrate separately. The results of simulations showed that layer-behavior model can predict drawing forces with more accuracy in comparison with single-behavior model. Also, mean friction coefficients used in FE-simulation signify the value that can occur maximum drawing force in a drawing test.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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• pp.529-539
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• 1998

A quantitative study of impact damage of ${Al_2}}O_3}-TiO_2$ plasma coated soda-lime glasses was carried out and compared with that of the uncoated smooth glass specimen. The shape of cracks by the impact of steel ball was observed by stereo-microscope and the decrease of the bending strength due to the impact of steel ball was measured through the 4-point bending test. At the low velocity, cone cracks were occurred. As the impact velocity increases, initial lateral cracks were propagated on the slanting surface of a cone crack, and radial cracks were generated at the crushed site. When the impact velocity of steel ball exceeds the critical velocity, the contact site of specimen was crushed due to plastic deformation and then radial and lateral cracks were largely grown. Crack length of coated specimens was smaller than that of uncoated smooth specimen due to the effect of coating layer on the substrate surface. According to impact velocity, the bending strength of coated specimens had no significant difference, compared with that of the uncoated smooth specimen. But this represents that the bending strength of coated specimens was increased, considering the effect of sand blasting damage which was performed to increase the adhesion force of coating layer.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.57 no.4
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• pp.449-455
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• 2012

Greenhouse and laboratory experiments were conducted to determine the effects of shade treatment and substrate components on plant growth and physiological activity of Taraxacum officinale. Substrates combined with coco peat and perlite (ratio 70 : 30 and 50 : 50, v/v) showed higher growth and yield than their single substrates (p<0.05). Shade treatment also significantly reduced plant height, root length, root diameter, leaf area, chlorophyll content, and fresh weight (p<0.05), compared to no shade. Contents of total phenolics [mg chlorogenic acid equivalents (CAE) $kg^{-1}$ DW] and total flavonoids [mg naringin equivalents $kg^{-1}$ DW] showed higher amounts in shoot parts than root parts of T. officinale, with shade than no shade. The antioxidant potential of the methanol extracts from the plants dose-dependently increased. DPPH (1,1-diphenyl-2-picryl hydrazyl radical) free radical scavenging activity was higher in leaf parts than in root parts of the plants, and no shade than with shade.

• Journal of Applied Tourism Food and Beverage Management and Research
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• v.13 no.1
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• pp.69-80
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• 2002

The grains were used as solid-substrate for the cultivation of basidiomycetes. The grains were fermented with Ganodema lucidum 7094, Fomitella fraxinea 81003, Phellinus igniarius 26005, and its free sugar composition was investigated. For the mass cultivation of mycelia, the hydrated grains with cold water were put into the plastic bottle. The mycelial growth rate in the bottled grains was high in the early stage with inoculation of homogenized mycelium. The activity of mycelium was maintained by adding sterilized water in the middle of cultivation. There was marked difference in the content of total free sugar and composition ratio of free sugar according to kinds of basidiomycetes. The content of free sugar increased far more in grains fermented with mycelium than in grains which was not fermented.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.305-308
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• 2006

Advanced mobile communication devices require a bright, high information content display in a small, light-weight, low power consumption package. For portable applications flexible (or conformable) and rugged displays will be the future. In this paper we outline our progress towards developing such a low power consumption active-matrix flexible OLED $(FOLED^{TM})$ display. We demonstrate full color 100 ppi QVGA active matrix OLED displays on flexible stainless steel substrates. Our work in this area is focused on integrating three critical enabling technologies. The first technology component is based on UDC's high efficiency long-lived phosphorescent OLED $(PHOLED^{TM})$ device technology, which has now been commercially demonstrated as meeting the low power consumption performance requirements for mobile display applications. Secondly, is the development of flexible active-matrix backplanes, and for this our team are employing PARC's Excimer Laser Annealed (ELA) poly-Si TFTs formed on metal foil substrates as this approach represents an attractive alternative to fabricating poly-Si TFTs on plastic for the realization of first generation flexible active matrix OLED displays. Unlike most plastics, metal foil substrates can withstand a large thermal load and do not require a moisture and oxygen permeation barrier. Thirdly, the key to reliable operation is to ensure that the organic materials are fully encapsulated in a package designed for repetitive flexing, and in this device we employ a multilayer thin film Barix encapsulation technology in collaboration with Vitex systems. Drive electronics and mechanical packaging are provided by L3 Displays.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05a
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• pp.189-192
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• 2004

To improvement life-time of the organic light emitting diodes(OLEDs). We investigate the inorganic composite film based on MgO and $SiO_2$ to protect from the moisture and oxygen. The inorganic composite films are added the base materials to the co-operate materials using the mixed process and it is deposited on plastic substrate by e-beam evaporator. In order to analyze as kinds of inorganic materials, Water Vapor method of Transmission Rate (WVTR) and Oxygen Transmission Rate (OTR) are measured by Permatran equipment(MOCON Corp.). For comparison. an MgD- and $SiO_2$-based composite film has lower values of WVTR and OTR than inorganic composite/compound films of ones. The results obtained here shows that this film is suitable for passivation layer to extend the life-time of OLEDs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.1
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• pp.12-16
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• 2011

In this study, we fabricated the flexible pentacene TFTs with the polymer gate dielectric and contact printing method by using the silver nano particle ink as a source/drain material on plastic substrate. In this experiment, to lower the cross-linking temperature of the PVP gate dielectric, UV-Ozone treatment has been used and the process temperature is lowered to $90^{\circ}C$ and the surface is optimized by various treatment to improve device characteristics. We tried various surface treatments; $O_2$ Plasma, hexamethyl-disilazane (HMDS) and octadecyltrichlorosilane (OTS) treatment methods of gate dielectric/semiconductor interface, which reduces trap states such as -OH group and grain boundary in order to improve the OTFTs properties. The optimized OTFT shows the device performance with field effect mobility, on/off current ratio, and the sub-threshold slope were extracted as $0.63cm^2 V^{-1}s^{-1}$, $1.7{\times}10^{-6}$, and of 0.75 V/decade, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.283-284
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• 2008

Electrical and optical characteristics of indium tin oxide (ITO) and indium zinc oxide (IZO) films without and with $(SiO_2)_3(ZnO)_7$ at.% (SZO) film deposited on poly(ethylene naphthalate) (PEN) and poly(ethylene terephthalate (PET) substrates as a gas barrier layer for flexible display were studied. The ITO and IZO films with SZO gas barrier layer showed the improved properties which were both the high transmittance of average 80% in the visible light range and the decreased sheet resistance as compared to those of ITO and IZO films without SZO layer. Particularly, the PEN substrate with only SZO gas barrier layer had a low water vapor transmission rate (WVTR) of $\sim10^{-3}g/m^2$/day. Thus, we suggest that the SZO film with protection ability against the water vapor permeation can be applied to gas barrier layer for flexible display.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.3
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• pp.15-20
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• 2007

Low temperature processed ZnO-TFTs on glass below $270^{\circ}C$ for plastic substrate applications were fabricated and their electrical properties were investigated. Films in ZnO-TFTs with bottom gate configuration were made by RF magnetron sputtering system except for $SiO_2$ gate oxide deposited by ICP-CVD. ZnO channel films were grown on glass with various Ar and $O_2$ flow ratios. All of the fabricated ZnO-TFTs showed perfectly the enhancement mode operation, a high optical transmittance of above 80% in visible ranges of the spectrum. In the ZnO-TFTs with pure Ar process, the field effect mobility, threshold voltage, and on/off ratio were measured to be $1.2\;cm^2/Vs$, 8.5 V, and $5{\times}10^5$, respectively. These characteristic values are much higher than those of the ZnO-TFTs of which ZnO channel layers were processed with additional $O_2$ gas. In addition, ZnO-TFT with pure Af process showed smaller swing voltage of 1.86v/decade compared to those with $Ar+O_2$ process.