• Journal of the Korean Vacuum Society
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• v.8 no.3A
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• pp.245-248
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• 1999

Recently low resistance of gate line or data line is required for large screen size TFT-LCD panels. As a result, lower resistance Al-alloy is currently reviewed extensively and the resistivity is required smaller than 10$\mu\Omega$cm. In this paper, Al-Nd and Al-Zr thin film were deposited on glass substrated by D.C. magnetron sputtering system under various condition. Its properties were characterized by SEM, AFM, XRD and 4-point-probe. The optimal condition was $120^{\circ}C$, 125W, 0.4Pa, 30sccm (Ar) and $350^{\circ}C$, 20min. annealing. At that condition the resistivity of Al-Zr(0.9%wt.) is about 4$\mu\Omega$cm.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.100-100
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• 2011

2004년 일본의 Hosono 그룹에 의해 처음 발표된 이래로, amorphous gallium-indium-zinc oxide (a-GIZO) thin film transistors (TFTs)는 높은 이동도와 뛰어난 전기적, 광학적 특성에 의해 큰 주목을 받고 있다. 또한 넓은 밴드갭을 가지므로 가시광 영역에서 투명한 특성을 보이고, 플라스틱 기판 위에서 구부러지는 성질에 의해 플랫 패널 디스플레이나 능동 유기 발광 소자(AM-OLED), 투명 디스플레이에 응용될 뿐만 아니라, 일반적인 Poly-Si TFT에 비해 백플레인의 대면적화에 유리하다는 장점이 있다. 최근에는 Y2O3나 ZrO2 등의 high-k 물질을 gate insulator로 이용하여 높은 캐패시턴스를 유지함과 동시에 낮은 구동 전압과 빠른 스위칭 특성을 가지는 a-GIZO TFT의 연구 결과가 보고되었다. 하지만 투명 디스플레이 소자 제작을 위해 플라스틱이나 유리 기판을 사용할 경우, 기판 특성상 공정 온도에 제약이 따르고(약 $300^{\circ}C$ 이하), 이를 극복하기 위한 부가적인 기술이 필수적이다. 본 연구에서는 p-type Si을 back gate로 하는 Inverted-staggered 구조의 a-GIZO TFT소자를 제작 하였다. p-type Si (100) 기판위에 RF magnetron sputtering을 이용하여 Gate insulator를 증착하고, 같은 방법으로 채널층인 a-GIZO를 70 nm 증착하였다. a-GIZO를 증착하기 위한 sputtering 조건으로는 100W의 RF power와 6 mTorr의 working pressure, 30 sccm Ar 분위기에서 증착하였다. 소스/드레인 전극은 e-beam evaporation을 이용하여 Al을 150 nm 증착하였다. 채널 폭은 80 um 이고, 채널 길이는 각각 20 um, 10 um, 5 um, 2 um이다. 마지막으로 Furnace를 이용하여 N2 분위기에서 $500^{\circ}C$로 30분간 후속 열처리를 실시한 후에, 전기적 특성을 분석하였다.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1580-1581
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• 2011

The linear accelerator of Pohang Accelerator Laboratory(PAL) will drive a top-up mode operation in PLS-II(Pohang Light Source-II). Due to this kind of the operation mode, the electron gun is expected to have shorter life time of the cathode. Further in the PLS-II, two gate valves will be installed in front of the electron gun. The distance between the pre-bunching section and the electron gun will increase by 400 mm compared to the existing system due to the insertion of these gate valves. As a result the incident electron beam. One of the goals to improve the beam pulse width is by incorporating suitable biased voltage. In this paper, we will present test results of beam pulse width as a function of different biased voltage and focusing solenoid coil.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.268-268
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• 2016

Chemical sensors have attracted much attention due to their various applications such as agriculture product, cosmetic and pharmaceutical components and clinical control. A conventional chemical and biological sensor is consists of fluorescent dye, optical light sources, and photodetector to quantify the extent of concentration. Such complicated system leads to rising cost and slow response time. Until now, the most contemporary thin film transistors (TFTs) are used in the field of flat panel display technology for switching device. Some papers have reported that an interesting alternative to flat panel display technology is chemical sensor technology. Recent advances in chemical detection study for using TFTs, benefits from overwhelming progress made in organic thin film transistors (OTFTs) electronic, have been studied alternative to current optical detection system. However numerous problems still remain especially the long-term stability and lack of reliability. On the other hand, the utilization of metal oxide transistor technology in chemical sensors is substantially promising owing to many advantages such as outstanding electrical performance, flexible device, and transparency. The top-gate structure transistor indicated long-term atmosphere stability and reliability because insulator layer is deposited on the top of semiconductor layer, as an effective mechanical and chemical protection. We report on the fabrication of InGaZnO TFTs with silver nanowire as the top gate electrode for the aim of chemical materials detection by monitoring change of electrical properties. We demonstrated that the improved sensitivity characteristics are related to the employment of a unique combination of nano materials. The silver nanowire top-gate InGaZnO TFTs used in this study features the following advantages: i) high sensitivity, ii) long-term stability in atmosphere and buffer solution iii) no necessary additional electrode and iv) simple fabrication process by spray.

• Journal of the Korean Vacuum Society
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• v.16 no.6
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• pp.414-423
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• 2007

Field Emission Display(FED) has significant advantages over existing display technologies, particularly in the area of small and high quality display. In order to test the feasibility of fabricating the System-on-Chip(SOC) with FED, we conducted the experiment to use the p-n junction as an electron beam source for the flat panel display. A novel structure was constructed to form p-n junctions by generating inversion layer with the electric field from the cantilever style gate. When we applied more than 220V at the cantilever style gate which has a height of $1{\mu}m$, avalanche breakdown onset was successfully achieved. The characteristics was compared with the electron emission from the ultra shallow junction in the avalanche region. The experiment result and the future direction were discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.163-163
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• 2015

The effect of nematic liquid crystal(5CB-4-Cyano-4'-pentylbiphenyl) on the amorphous indium gallium zinc oxide thin film transistors(a-IGZO TFTs) was investigated. Through dropping the 5CB on the a-IGZO TFT's channel layer which is deposited by RF-magnetron sputtering, properties of a-IGZO TFTs was dramatically improved. When drain bias was induced, 5CB molecules were oriented by Freedericksz transition generating positive charges to one side of dipoles. From increment of the capacitance by orientation of liquid crystals, the drain current was increased, and we analyzed these phenomena mathematically by using MOSFET model. Transfer characteristic showed improvement such as decreasing of subthreshold slope(SS) value 0.4 to 0.2 and 0.45 to 0.25 at linear region and saturation region, respectively. Furthermore, in positive bias system(PBS), prevention effect for electron trapping by 5CB liquid crystal dipoles was observed, which showing decrease of threshold voltage shift [(${\delta}V$]_TH) when induced +20V for 1~1000sec at the gate electrode.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1303-1308
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• 2004

This paper proposes a reduction method for the mis-operation analysis of the DC High Speed Circuit Breaker(HSCB) in electric railway substation system. The analysis method is based on present condition of operation which is a method for accuracy level up. There is reason to operation of HSCB that it is mis-operation of fault detection relay(50F), operation of ground fault relay(64P), and trouble of electric car. A countermeasure is relay resetting through field test, induction of GTOCB(Gate Turn Off Thyristor Circuit Breaker), HSVCB(High Speed Vacuum Circuit Breaker), coordination with electric car. The results presented in the paper can be used as a reference for maintenance free in electric railway substation system.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.128.1-128.1
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• 2016

Nitrided-metal gates on the high-${\kappa}$ dielectric material are widely studied because of their use for sub-20nm semiconductor devices and the academic interest for the evanescent states at the Si/insulator interface. Issues in these systems with the Si substrate are the electron mobility degradation and the reliability problems caused from N defects that permeates between the Si and the $SiO_2$ buffer layer interface from the nitrided-gate during the gate deposition process. Previous studies proposed the N defect structures with the gap states at the Si band gap region. However, recent experimental data shows the possibility of the most stable structure without any N defect state between the bulk Si valence band maximum (VBM) and conduction band minimum (CBM). In this talk, we present a new type of the N defect structure and the electronic structure of the proposed structure by using the first-principles calculation. We find that the pair structure of N atoms at the $Si/SiO_2$ interface has the lowest energy among the structures considered. In the electronic structure, the N pair changes the eigenvalue of the silicon-induced gap state (SIGS) that is spatially localized at the interface and energetically located just above the bulk VBM. With increase of the number of N defects, the SIGS gradually disappears in the bulk Si gap region, as a result, the system gap is increased by the N defect. We find that the SIGS shift with the N defect mainly originates from the change of the kinetic energy part of the eigenstate by the reduction of the SIGS modulation for the incorporated N defect.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.254-254
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• 2011

The memories with nano-particles are very attractive because they are promising candidates for low operating voltage, long retention time and fast program/erase speed. In recent, various nano-floating gate memories with metal-oxide nanocrystals embedded in organic and inorganic layers have been reported. Because of the carrier generation in semiconductor, induced photon pulse enhanced the program/erase speed of memory device. We studied photo-induced electrical properties of these metal-oxide nanocrystal memory devices. At first, 2~10-nm-thick Sn and In metals were deposited by using thermal evaporation onto Si wafer including a channel with $n^+$ poly-Si source/drain in which the length and width are 10 ${\mu}m$ each. Then, a poly-amic-acid (PAA) was spin coated on the deposited Sn film. The PAA precursor used in this study was prepared by dissolving biphenyl-tetracarboxylic dianhydride-phenylene diamine (BPDA-PDA) commercial polyamic acid in N-methyl-2-pyrrolidon (NMP). Then the samples were cured at 400$^{\circ}C$ for 1 hour in N atmosphere after drying at 135$^{\circ}C$ for 30 min through rapid thermal annealing. The deposition of aluminum layer with thickness of 200 nm was followed by using a thermal evaporator, and then the gate electrode was defined by photolithography and etching. The electrical properties were measured at room temperature using an HP4156a precision semiconductor parameter analyzer and an Agilent 81101A pulse generator. Also, the optical pulse for the study on photo-induced electrical properties was applied by Xeon lamp light source and a monochromator system.

• Electrical & Electronic Materials
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• v.10 no.10
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• pp.1029-1033
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• 1997

A prototype MFSFET using ferroelectric fluoride BaMgF$_4$as a gate insulator has been successfully fabricated with the help of 2 sheets of metal mask. The fluoride film was deposited in an ultrai-high vacuum system at a substrate temperature of below 30$0^{\circ}C$ and an in-situ post-deposition annealing was conducted for 20 seconds at $650^{\circ}C$ in the same chamber. The interface state density of the BaMgF$_4$/Si(100) interface calculated by a MFS capacitor fabricated on the same wafer was about 8$\times$10$^{10}$ /cm$^2$.eV. The I$_{D}$-V$_{G}$ characteristics of the MFSFET show a hysteresis loop due to the ferroelectric nature of the BaMgF$_4$film. It is also demonstrated that the I$_{D}$ can be controlled by the “write” plus which was applied before the measurements even at the same “read”gate voltage.ltage.