• Electrical & Electronic Materials
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• v.8 no.5
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• pp.619-625
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• 1995

Polycrystalline CdTe thin film has been studied for photovoltaic application due to the 1.45 eV band gap energy ideal for solar energy conversion and high absorption coefficient. The formation of low resistance contact to p-CdTe is difficult because of large work function(>5.5eV). Common methods for ohmic contact to p-CdTe are to form a p+ region under the contact by in-diffusion of contact material to reduce the barrier height and modify a p-CdTe surface layer using chemical treatment. In this study, the surface chemical treatment of p CdTe was carried out by H$\_$3/PO$\_$4/+HNO$\_$3/ or K$\_$2/Cr$\_$2/O$\_$7/+H$\_$2/SO$\_$4/ solution to provide a Te-rich surface. And various thin film contact materials such as Cu, Au, and Cu/Au were deposited by E-beam evaporation to form ohmic contact to p-CdTe. After the metallization, post annealing was performed by oven heat treatment at 150.deg. C or by RTA(Rapid Thermal Annealing) at 250-350.deg. C. Surface chemical treatments of p-CdTe thin film improved metal/p-CdTe interface properties and post heat treatment resulted in low contact resistivity to p-CdTe.Of the various contact metal, Cu/Au and Cu show low contact resistance after oven and RTA post-heat treatments, respectively.

• The Journal of the Korea Contents Association
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• v.7 no.2
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• pp.92-99
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• 2007

This paper presented a low power design of a 32bit block cypher processor reduced from the original 128bit architecture. The primary purpose of this research is to evaluate physical implementation results rather than theoretical aspects. The data path and diffusion function of the processor were reduced to accommodate the smaller hardware size. As a running example demonstrating the design approach, we employed a modified ARIA algorithm having four S-boxes. The proposed 32bit ARIA processor comprises 13,893 gates which is 68.25% smaller than the original 128bit structure. The design was synthesized and verified based on the standard cell library of the MagnaChip's 0.35um CMOS Process. A transistor level power simulation shows that the power consumption of the proposed processor reduced to 61.4mW, which is 9.7% of the original 128bit design. The low power design of the block cypher Processor would be essential for improving security of battery-less wireless sensor networks or RFID.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.6
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• pp.1169-1174
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• 2011

CdTe thin-film solar cell technology is well known that it can theoretically improve its conversion efficiency and manufacturing costs compared to the conventional silicon solar cell technology, due to its optical band gap energy (about 1.45eV) for solar energy absorption, high light absorption capability and low cost requirements for producing solar cells. Although the prior studies obtained the high light absorption, CdTe thin film solar cell has not been come up to the sufficient efficiency yet. So, doping method was selected for the improvement of the electrical characteristics in CdTe solar cells. Some elements including Cu, Ag, Cd and Te were generally used for the p-dopant as substitutional acceptors in CdTe thin film. In this study, the sputtering-deposited CdTe thin film was immersed in $AgNO_3$ solution for ion exchange method to dope Ag ions. The effects of immersion temperature and Ag-concentration were investigated on the optical properties and electrical characteristics of CdTe thin film by using Auger electron spectroscopy depth-profile, UV-visible spectrophotometer, and a Hall effect measurement system. The best optical and electrical characteristics were sucessfully obtained by Ag doping at high temperature and concentration. The larger and more uniform diffusion of Ag ions made increase of the Ag ion density in CdTe thin film to decrease the series resistance as well as mede the faster diffusion of light by the metal ions to enhance the light absorption.

• Journal of Life Science
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• v.17 no.11
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• pp.1517-1522
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• 2007

Gap junction channels formed by two adjacent cells allow the passage of small molecules up to ${\sim}\;1\;kDa$ between them. Hemichannel (connexon or half of gap junction) also behaves as a membrane channel like sodium or potassium channels in a single cell membrane. Among 26 types of connexin (Cx), $Cx32^*43E1$ (a chimera in which the first extracellular loop of Cx32 has been replaced with that of Cx43), Cx38, Cx46, and Cx50 form functional hemichannels as well as gap junction channels. Although it is known that Xenopus oocytes express endogenous connexin 38 (Cx38), its biophysical characteristics at single channel level are poorly understood. In this study, we performed single channel recordings from single Xenopus oocytes to acquire the biophysical properties of Cx38 including voltage-dependent gating and permeation (conductance and selectivity). The voltage-dependent fast and slow gatings of Cx38 hemichannel are distinct. Fast gating events occur at positive potentials and their open probabilities are low. In contrast, slow gatings dominate at negative potentials with high open probabilites. Based on hi-ionic experiments, Cx38 hemichannel is anion-selective. It will be interesting to test whether charged amino acid residues in the amino terminus of Cx38 are responsible for voltage gatings and permeation.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.394-394
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• 2011

급속한 산업의 발달은 심각한 환경오염 및 에너지 문제를 가져왔다. 이를 해결하기 위하여 무한한 에너지원인 태양에너지를 원천으로 하는 친환경 정화소재로서의 광촉매(photocatalyst)를 통하여 인류의 에너지를 확보하는 것에 대한 관심이 급격하게 증가하고 있는 추세이다. 현재 광촉매로 가장 많이 사용되는 $TiO_2$의 경우 뛰어난 광활성과 저렴한 가격, 광 안정성, 화학적 안정성을 가짐에도 불구하고, 3.2 eV라는 상대적으로 넓은 band gap을 가지기 때문에 약 386 nm보다 짧은 파장을 갖는 자외선만 흡수할 수 있다. 이로 인한 가시광 응답성의 부재를 해결하기 위해 수십년간 많은 연구가 진행되어 왔다. 따라서 본 연구에서는 ICP assisted pulsed DC reactive magnetron sputtering을 이용하여 $TiO_2$를 기반으로 하면서 가시광영역의 빛을 흡수하여 높은 효율을 얻을 수 있도록 Nitrogen doping, Low band gap semi-conductor sensitization 등의 방법을 사용하여 광촉매를 제작하였다. 시료의 chemical state와 crystallinity를 확인하기 위하여 X-ray photoelectron spectroscopy와 X-ray diffraction method를 이용하여 분석을 수행하였으며, 이러한 공정을 통해 제작된 $TiO_2$기반 광촉매의 가시광 응답성을 확인하기 위하여 UV/Vis 스펙트럼을 측정하였다. 또한 물 분해 장치(water splitting device)를 제작하여 수소와 산소 생성시 흐르는 전류를 측정하여 광특성을 평가하였다.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.489-492
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• 2005

We report new polymer stabilized ferroelectric liquid crystal (PSFLC) cells with mechanical stability which is achievable by introducing photospacers in the cells. It was found that the mechanical st ability of the PSFLC cell was effected by introduction of photo spacers. We analyzed the dependence of mechanical stability and memory property on the density of photospacers in the PSFLC cell. The stability and memory properties of PSFLC Cells depending on photospacer density are discussed. 1. Introduction Recently, flexible displays have attracted much attention because they have remarkable advantages: thinner, lighter, non-breakable and conformable features. Flexible displays have various potential applications such as e-book and e-paper displays utilizing the distinct features. E-book and E-paper displays demand very low power consumption, so that bistable memory liquid crystal modes are required in case of flexible plastic LCDs for those application. Three kinds of memory LC modes have been developed; bistable nematic, bistable cholesteric and bistable FLC. Among them SSFLC as one of bistable FLC has big advantages such as low driving voltage, wide view angle and fast response time, SSFLC cells are, however, very weak against mechanical shock. Polymer stabilized FLC (PSFLC) has been developed to overcome the poor mechanical stability of SSFLC. PSFLC was known to have network structure that FLCs are oriented with smectic layer ordering in polymer network. The polymer network stabilizes the FLC orientation, which leads to improvement of mechanical stability of PSFLCD. A lot of studies have been done for the application of PSFLC to flexible $LCDs.^{[1{\sim}12]}$ However, it should be noted that PSFLC does not have sufficient mechanical stability for the particular applications such as smart card LCD, where LCD is highly bendable.Bead spacer was mainly used to maintain cell gap of conventional PSFLCDs. But the spacer density of it is not locally uniform in the cell, so that it is generally difficult that the PSFLCDs with bead spacers show sufficient mechanical stability. In order to more improve the mechanical stability of PSFLCDs, we introduced photospacers into PSFLCDs. In this paper, we describe the improvement of mechanical stability by introducing photospacers into PSFLCDs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.5
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• pp.355-358
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• 2011

As a II-IV compound semiconductor, ZnO has a wide band gap of 3.37 eV with transparent properties. Due to this transparent properties, ZnO materials can be also employed as the transparent conducting electrode materials. Recently, rapid progress has been made in the field of DSSC (dye sensitized solar cell)area. Therefore, strong demands have been required for the transparent electrodes with low temperature processing and cheap cost. In this paper, we will prepare ZnO thick films on the PET substrates for the electrode applications. We will investigate the structural and microstructure properties through the XRD, and SEM analysis, respectively. Also, we will study the electrical of specimens to apply the conducting electrode.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1384-1391
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• 2001

Three-dimensional flow analysis is implemented to investigate the flow through transonic axial-flow compressor rotor(NASA R67) and to evaluate the performances of Abid's low-Reynolds-number k-$\omega$ and Baldwin-Lomax turbulence models. A finite volume method is used fur spatial discretization. The equations are solved implicitly in time by the use of approximate factorization. The upwind difference scheme is used for inviscid terms and viscous terms are approximated with central difference. The flux-difference-splitting method of Roe is used to obtain fluxes at the cell faces. Numerical analysis is performed near peak efficiency and near stall. The results are compared with the experimental data for NASA R67 rotor. Blade-to-Blade Mach number distributions are compared to confirm the accuracy of the code. From the results, it is concluded that Abid'k-$\omega$ model is better for the calculation of flow rate and efficiency than Baldwin-Lomax model. But, the predictions for Mach number and shock structure are almost the same.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.19.1-19.1
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• 2010

The process of manufacturing printed electronics using printing technology is attracting attention because its process cost is lower than that of the conventional semiconductor process. This technology, which offers both a lower cost and higher productivity, can be applied in the production of organic TFT (thin film transistor), solar cell, RFID(radio frequency identification) tag, printed battery, E-paper, touch screen panel, black matrix for LCD(liquid crystal display), flexible display, and so forth. In general, in order to implement printed electronics, narrow width and gap printing, registration of multi-layer printing by several printing units, and printing accuracy of under $20\;{\mu}m$ are all required. These electronic products require high precision to the degree of tens of microns - in a large area with flexible material, and mass productivity at low cost. As such, the roll-to-roll printing process is attracting attention as a mass production system for these printed electronic devices. For the commercialization of this process, two basic electronic ink technologies, such as conductive ink and polymers, and printing equipment have to be developed. Therefore, this paper addressed basis design and test to develop fine patterning equipment employing the roll-to-roll printing equipment and electronic ink.

• Journal of the Korean Chemical Society
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• v.60 no.3
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• pp.194-202
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• 2016

Two conjugated semiconducting copolymers consisting of 4,7-bis(4-(2-ethylhexyl)-2-thiophene)-2,1,3-benzothiadiazole (DTBT) and benzo[1,2-b:4,5-b']dithiophene with 5-(2-ethylhexyl)-2,2'-bithiophene (BDTBT) or 5-(2-ethylhexylthio)- 2,2'-bithiophene (BDTBT-S) were designed and synthesized as donor materials for organic photovoltaic cells (OPVs). Alkylthio-substituted PBDTBT-S-DTBT showed a higher hole mobility and lower highest occupied molecular orbital (HOMO) energy level (by 0.08 eV) than the corresponding alkyl-substituted PBDTBT-DTBT. An OPV fabricated using PBDTBT-S-DTBT showed higher V_OC and J_SC values of 0.83 V and 7.56 mA/cm², respectively, than those of a device fabricated using PBDTBT-DTBT (0.74 V) leading to a power conversion efficiency of 2.05% under AM 1.5G 100 mW/cm² illumination.