• Journal of Information Display
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• v.4 no.1
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• pp.29-33
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• 2003

We have investigated the effects of hole-injection buffer layer in organic light-emitting diodes using copper phthalocyanine (CuPc), poly(vinylcarbazole)(PVK), and Poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT: PSS) in a device structure of $ITO/bufferr/TPD/Alq_3/Al$. Polymer PVK and PEDOT:PSS buffer layer were produced using the spin casting method where as the CuPc layer was produced using thermal evaporation. Current-voltage characteristics, luminance-voltage characteristics and efficiency of device were measured at room temperature at various a thickness of the buffer layer. We observed an improvement in the external quantum efficiency by a factor of two, four, and two and half when the CuPc, PVK, and PEDOT:PSS buffer layer were used, respectively. The enhancement of the efficiency is assumed to be attributed to the improved balance of holes and elelctrons resulting from the use of hole-injection buffer layer. The CuPc and PEDOT:PSS layer function as a hole-injection supporter and the PVK layer as a hole-blocking one.

• Journal of Communications and Networks
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• v.12 no.3
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• pp.275-284
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• 2010

The current multihome-aware protocols (like stream control transmission protocol (SCTP) or parallel TCP for concurrent multipath data transfer (CMT) are not designed for high-capacity and large-latency networks; they often have performance problems transferring large data files over shared long-distance wide area networks. It has been shown that SCTP-CMT is more sensitive to receive buffer (rbuf) constraints, and this rbuf-blocking problem causes considerable throughput loss when multiple paths are used simultaneously. In this research paper, we demonstrate the weakness of SCTP-CMT rbuf constraints, and we then identify that rbuf-blocking problem in SCTP multihoming is mostly due to its loss-based nature for detecting network congestion. We present a simulation-based performance comparison of FAST TCP versus SCTP in high-speed networks for solving a number of throughput issues. This work proposes an end-to-end transport layer protocol (i.e., FAST TCP multihoming as a reliable, delaybased, multihome-aware, and selective ACK-based transport protocol), which can transfer data between a multihomed source and destination hosts through multiple paths simultaneously. Through extensive ns-2 simulations, we show that FAST TCP multihoming achieves the desired goals under a variety of network conditions. The experimental results and survey presented in this research also provide an insight on design decisions for the future high-speed multihomed transport layer protocols.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1579-1581
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• 1996

The high temperature characteristics of SOI BMFET are analyzed by the numerical simulation and compared with MOS-gated SOI power devices at high temperatures. The proposed SOI BMFET combines bipolar operation in the on-state with unipolar FET operation in the off-state, so that it may be suitable for high temperature operation without any significant degradation of performance such as the leakage current and blocking capability. The simulation results show that SOI BMFET with a higher doped n-resurf layer is the most promising device far high temperature application as compared with MOS-gated SOI power devices, exhibiting the low on-state voltage drop as well as the excellent forward blocking capability at high temperature.

• Transactions on Electrical and Electronic Materials
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• v.12 no.4
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• pp.148-151
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• 2011

We designed and fabricated aluminium gallium nitride (AlGaN)/GaN high electron mobility transistors (HEMTs) with stable reverse blocking characteristics established by employing a selective fluoride plasma treatment on the drainside gate edge region where the electric field is concentrated. Implanted fluoride ions caused a depolarization in the AlGaN layer and introduced an extra depletion region. The overall contour of the depletion region was expanded along the drift region. The expanded depletion region distributed the field more uniformly and reduced the field intensity peak. Through this field modulation, the leakage current was reduced to 9.3 nA and the breakdown voltage ($V_{BR}$) improved from 900 V to 1,400 V.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.136-136
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• 2011

반도체 및 전자기기 산업에 있어서 NVM은 아주 중요한 부분을 차지하고 있다. NVM은 디스플레이 분야에 많은 기여를 하고 있는데, 측히 AMOLED에 적용이 가능하여 온도에 따라 변하는 구동 전류, 휘도, color balance에 따른 문제를 해결하는데 큰 역할을 한다. 본 연구에서는 bottom gate 구조의 nc-Si NVM 실험을 진행하였다. P-type silicon substrate (0.01~0.02 ${\Omega}-cm$) 위에 Blocking layer 층인 SiO2 (SiH4:N2O=6:30)를 12.5nm증착하였고, Charge trap layer 층인 SiNx (SiH4:NH3=6:4)를 20 nm 증착하였다. 마지막으로 Tunneling layer 층인 SiOxNy은 N2O (2.5 sccm) 플라즈마 처리를 통해 2.5 nm 증착하였다. 이러한 ONO 구조층 위에 nc-Si을 50 nm 증착후에 Source와 Drain 층을 Al 120 nm로 evaporator 이용하여 증착하였다. 제작한 샘플을 전기적 특성인 Threshold voltage, Subthreshold swing, Field effect mobility, ON/OFF current ratio, Programming & Erasing 특성, Charge retention 특성 등을 알아보았다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.311-312
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• 2010

The fabricated photovoltaic cells based on PIN heterojunctions, in this study, have a structure of ITO/poly(3, 4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS)/donor/donor:C60(10nm)/C60(35nm)/2, 9-dimethyl-4, 7-diphenyl-1, 10-phenanthroline(8nm)/Al(100nm). The thicknesses of an active layer(donor:C60), an electron transport layer(C60), and hole/exciton blocking layer(BCP) were fixed in the organic photovoltaic cells. We investigated the performance characteristics of the PIN organic photovoltaic cells with copper phthalocyanine(CuPc), tetracene and pentacene as a hole transport layer. Discussion on the photovoltaic cells with CuPc, tetracene and pentacene as a hole transport layer is focussed on the dependency of the power conversion efficiency on the deposition rate and thickness of hole transport layer. The device performance characteristics are elucidated from open-circuit-voltage(Voc), short-circuit-current(Jsc), fill factor(FF), and power conversion efficiency($\eta$). As the deposition rate of donor is reduced, the power conversion efficiency is enhanced by increased short-circuit-current(Jsc). The CuPc-based PIN photovoltaic cell has the limited dependency of power conversion efficiency on the thickness of hole transport layer because of relatively short exciton diffusion length. The photovoltaic cell using tetracene as a hole transport layer, which has relatively long diffusion length, has low efficiency. The maximum power conversion efficiencies of CuPc, tetracene, and pentacene-based photovoltaic cells with optimized deposition rate and thickness of hole transport layer have been achieved to 1.63%, 1.33% and 2.15%, respectively. The photovoltaic cell using pentacene as a hole transport layer showed the highest efficiency because of dramatically enhanced Jsc due to long diffusion length and strong thickness dependence.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.1
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• pp.329-332
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• 2012

LEDs are using widely in a field of illumination, LCD LED backlight, mobile signals because they have several merits, such as low power consumption, long lifetime, high brightness, fast response, environment friendly. To achieve high performance LEDs, one needs to enhance output power, reduce operation voltage, and improve device reliability. In this paper, we have proposed that the optimum design and specialized process could improve the performance of LED chip. It was showed an output power of 7cd and input supplied voltage of 3.2V by the insertion technique of current blocking layer. In this paper, GaN-based LED chip which is built on the sapphire epi-wafer by selective MOCVD were designed and developed. After that, their performances were measured. It showed the output power of 7cd more than conventional GaN-based chip. It will be used the lighting source of a medical equipment and LCD LED TV with GaN-based LED chip.

• 전자공학회논문지 IE
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• v.43 no.4
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• pp.1-7
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• 2006

In this paper, two types of blue organic light-emitting device were designed. We have analyzed the characteristics of Type I device without a hole blocking layer, and analyzed the characteristics of Type II device using a hole blocking layer of BCP or BAlq materials with 30 ${\AA}$ thickness. We obtained the ITO having the work function value of 5.02 eV using $N_2$ plasma treatment method with the plasma power 200 W. Type I device structure was ITO/2-TNATA/$\alpha$-NPD/DPVBi/$Alq_3$/LiF/Al:Li, and type II device structure was ITO/2-TNATA/$\alpha$-NPD/DPVBi/HBL/$Alq_3$/LiF/Al:Li. We have analyzed the characteristics of Type I and Type II device. The characteristics of the device were most efficiency on occasion of using a hole blocking layer of BAlq material with 30 ${\AA}$ thickness. Current density was 226.75 $mA/cm^2$, luminance was 10310 $cd/m^2$, Current efficiency was 4.55 cd/A, power efficiency was 1.43 lm/W at an applied voltage of 10V. The maximum EL wavelength of the fabricated blue organic light-emitting device was 456nm. The full-width at half-maximum (FWHM) for the EL spectra was 57nm. CIE color coordinates were x=0.1438 and y=0.1580, which was similar to NTSC deep-blue color with CIE color coordinates of x=0.14 and y=0.08.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1070-1073
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• 2003

We have studied the characteristics of organic light-emitting diodes(OLEDs) with the PTFE buffer layer. The OLEDs have been based on the molecular compounds, N,N'-diphenyl-N,N'-bis (3-methylphenyl)-1, 1'- biphenyl-4, 4'-diamine (TPD) as a hole transport, tris(8-hydroxyquinolinoline) aluminum (III) ($Alq_3$) as an electron transport and the Polytetrafluoroethylene (PTFE) as a buffer layer. The devices of structure were fabricated ITO/PTFE/TPD(40nm)/$Alq_3$(60nm)/Al( 150nm) to see the effects of the PTFE buffer layer in organic EL devices. The thickness of the PTFE layer varied from 0.5 to 10[nm]. We were measured Current-Voltage-Luminance Characteristics and Luminance efficiency due to the variation of PTFE thickness. the PTFE layer was reported that helped to enhance the hole tunneling injection and effectively impede induim diffusion from the ITO electrode. We have obtained an improvement of luminance efficiency when the PTFE thickness is 0.5[nm] is used. The improvement of efficiency of is expected due to a function of hole-blocking of PTFE in OLEDs.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.29-39
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• 2010

By understanding the construction process of sea dikes and the current state of the thickness and speed of fluid in the bottom layer protection work of final closure gaps, a construction method applicable for the blocking of bottom layer work will be selected. The three construction methods selected will be tested in site through various methods, and the reinforcement of bottom layer protection and impervious effect will be verified. The verification results are as follows: 1) The overall riprap layer were 0.5~1.0m thicker than planned so that the grouting depth and grout input amount increased 2) The applied construction methods permeability of riprap layers were improved from $\alpha{\times}10^{-2}cm/s$ before the construction to $\alpha{\times}10^{-4}cm/s$ after construction. 3) The results of core extraction in order to grossly verify the hardening time and durability allowed the identification of grout injection effect. The amount of filling of the injection was difficult to judge because the slime in many areas made the reading of borehole photography difficult.