• 한국전기전자재료학회논문지
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• 제33권2호
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• pp.155-160
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• 2020

Ga₂O₃/n-type 4H-SiC heterojunction diodes were fabricated by RF magnetron sputtering. The optical properties of Ga₂O₃ and electrical properties of diodes were investigated. I-V characteristics were compared with simulation data from the Atlas software. The band gap of Ga₂O₃ was changed from 5.01 eV to 4.88 eV through oxygen annealing. The doping concentration of Ga₂O₃ was extracted from C-V characteristics. The annealed oxygen exhibited twice higher doping concentration. The annealed diodes showed improved turn-on voltage (0.99 V) and lower leakage current (3 pA). Furthermore, the oxygen-annealed diodes exhibited a temperature cross-point when temperature increased, and its ideality factor was lower than that of as-grown diodes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.267-269
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• 2007

PLL(Phase Locked Loop) are widely used circuit technique in modern electronic systems. In this paper, We propose the low voltage and high speed PLL. We design the PFD(Phase Frequency Detector) by using TSPC (True Single Phase Clock) circuit to improve the performance and solve the dead-zone problem. We use CP(Charge Pump} and LP(Loop filter) for Negative feedback and current reusing in order to solve current mismatch and switch mismatch problem. The VCO(Voltage controlled Oscillator) with 5-stage differential ring oscillator is used to exact output frequency. The divider is implemented by using D-type flip flops asynchronous dividing. The frequency divider has a constant division ratio 32. The frequency range of VCO has from 200MHz to 1.1GHz and have 1.7GHz/v of voltage gain. The proposed PLL is designed by using 0.18um CMOS processor with 1.8V supply voltage. Oscillator's input frequency is 25MHz, VCO output frequency is 800MHz and lock time is 5us. It is evaluated by using cadence spectra RF tools.

• 대한기계학회논문집A
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• 제27권11호
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• pp.1849-1855
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• 2003

Newly commercialized wireless capsule endoscope has many advantages compared to conventional push-type endoscopes. However, it is moved by the peristaltic waves. Therefore, it can not diagnose desired zones actively. In this paper, a locomotive mechanism for wireless capsule endoscope is proposed to increase the efficiency of endoscopy. We designed and fabricated a prototype using SMA springs and bio-mimetic clamping device. The hollow space in the prototype is allocated for further system integration of a camera module, a RF module and a battery. And the sequential control scheme is employed to improve the efficiency of its locomotion. To validate the performance of the locomotive mechanism, experiments on a silicone rubber pad and in vitro tests are carried out. The results of the experiments indicate that proposed mechanism is effective in harsh environments such as digestive organs of a human.

• 한국정보통신학회논문지
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• 제10권4호
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• pp.739-743
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• 2006

본 논문은 신경회로망을 이용한 화자적응 음성인식 제어시스템을 개발하였다. 화자종속시스템은 단일 화자의 음성만 등록하여 이용하므로 여러 화자의 음성을 인식하는 데는 문제가 있고, 화자독립시스템은 여러 화자를 인식한다. 본 연구 개발에서는 화자적응시스템을 구현하여 화자종속형의 단점을 보완하여 화자 독립과 화자 종속을 혼합하여 사용 할 수 있는 기능으로 화자 적용방법으로 구현하였고, 화자인증(Speaker Verification)도 가능하도록 프로그램 하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.205-205
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• 2010

기존의 박막트랜지스터에 비하여 대면적의 박막 형성이 용이하고 높은 이동도의 특성을 가지는 ZnO는 상온에서 높은 밴드갭 에너지(3.4eV)와 엑시톤 결합에너지(60meV)로 인해 가시광영역을 투과시킬 뿐만 아니라 가시광으로 인해 유도되는 광 캐리어가 생성되어 열화되는 현상이 없는 장점을 가지고 있다. 또한 다른 물질에 비해 높은 이동도($1{\sim}100\;cm2/V{\cdot}s$)로 인해 기존의 실리콘 기반의 박막트랜지스터를 대체할 수 있는 물질로 최근 주목 받고 있다. 이러한 ZnO는 접합된 소스와 드레인 전극의 Work function 및 resistivity의 차이에 따라 전기적 특성에도 많은 변화가 생기게 된다. 본 연구에서는 박막트랜지스터의 전극에 이용되는 금속에 변화를 주어 이에 따른 전기적 특성에 대해 연구하였다. 이를 위해 먼저, P-type 실리콘 위에 습식 방법으로 SiO2를 300nm성장 시켰고, ZnO 박막을 Sputtering 방식으로 증착하여 트랜지스터를 제작하였다. 그리고 소자의 소스와 드레인 전극으로 사용되는 금속은 E-beam evaporator과 RF Magnetron Sputter를 이용하여 증착하였다. 또한 금속의 Work function을 확인하기 위해 Capacitor를 제작하여 이에 대한 Capacitance-Voltage 특성과 함께, 박막트랜지스터의 Current-Voltage 특성을 확인해 보았다. 이와 같이 소스와 드레인 전극의 최적화된 Material을 이용하여 전기적 특성이 향상된 박막트랜지스터 소자를 기대할 수 있다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.364.1-364.1
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• 2014

고효율 태양전지로 가기 위해서는 태양전지의 후면 패시베이션은 중요한 역할을 한다. 후면 패시베이션 막으로 사용되는 $Al_2O_3$ 막은 $Al_2O_3/Si$ 계면에서 높은 화학적 패시베이션과 Negative Fixed Charge를 가지고 있어 적합한 Barrier막으로 여겨진다. 하지만 이후에 전면 Metal paste의 소성 공정에 의해 $800^{\circ}C$이상 온도를 올려주게 됨에 따라 $Al_2O_3$ 막 내부에 결합되어 있던 수소들이 방출되어 blister가 생성되고 막 질은 떨어지게 된다. 우리는 blister가 생성되는 것을 방지하기 위한 방법으로 PECVD 장비로 SiNx를 증착하는 공정 중에 $N_2O$ 가스를 첨가하여 SiON 막을 증착하였다. SiON막은 $N_2O$가스량을 조절하여 막의 특성을 변화시키고 변화에 따라 소성시 막에 미치는 영향에 대하여 조사하였다. 공정을 위해 $156{\times}156mm2$, $200{\mu}m$, $0.5-3.0{\Omega}{\cdot}cm$ and p-type 단결정 실리콘 웨이퍼를 사용하였고, $Al_2O_3$ 막을 올리기 전에 RCA Cleaning 실행하였다. ALD 장비를 통해 $Al_2O_3$ 막을 10nm 증착하였고 RF-PECVD 장비로 SiNx막과 SiON막을 80nm 증착하였다. 소성로에서 $850^{\circ}C$ ($680^{\circ}C$) 5초동안 소성하고 QSSPC를 통해 유효 반송자 수명을 알아보았다.

• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.372-377
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• 2014

Being able to monitor the heart will allow the diagnosis of heart diseases for patients during daily activities, and the detection of burden on the heart during strenuous exercise. Furthermore, with the help of U-health technology, immediate medical action can be taken, in the case of abnormal symptoms of the heart in daily life. Therefore, it appears to be necessary to develop the corresponding technology to monitor the condition of the heart daily. In this study, a novel wearable smart system was proposed, to monitor the activity of the heart in daily life, and to further evaluate the rhythm of arrhythmia. The wearable system includes three modified bipolar conductive fiber electrodes in the chest part, which can resolve the reduction problem of the magnitude of the signal, by magnifying the signal and removing the noise, to obtain high affinity and validity for medical-type usage (<0.903%). The biological signal acquisition and data lines, and the signal processing engine and communication consist of a conductive ink, and the pic18 and ANT protocol nRF24AP2, respectively. The proposed algorithm was able to detect a strong ECG, signal and r-point passing over the noise. The confidence intervals were 96 %, which could satisfy the requirement to detect arrhythmia under the unconstrained conditions.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 일렉트렛트 및 응용기술
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• pp.58-62
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• 2002

Pb($Zr_{0.52}Ti_{0.48}$)$O_3$ (PZT) thin films deposited on the Pt/Ti and Ru/$RuO_2$ bottom electrode by rf magnetron sputtering methode. Ru/$RuO_2$ bottom electrode deposited on the p-type wafer as Ru thickness by in-situ process. Our results show that all PZT films indicated perovskite polycrystalline structure with perferred orientation (110) and no pyrochlore phase is observed. A well-fabricated $RuO_2$/PZT/Ru(100nm)/$RUO_2$ capacitor showed a leakage current density in the order of $2.13{\times}10^{-7}A/cm^2$ as 100 kV/cm, a remanent polarization of 7.20 ${\mu}C/cm^2$, and a coercive field of 58.37 kV/cm. The results show that the new Ru/$RuO_2$ bottom electrodes are expected to reduce the degradation ferroelectric fatigue and excellent ferroelectric properties.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.633-636
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• 2007

The objective of this study is to measure backscattering coefficients of paddy rice using L, C, X-bands scatterometer system during a rice growth period. The measurement was conducted at an experimental field located in National Institute of Agricultural Science and Technology (NIAST), Suwon, Korea. The rice cultivar was a kind of Japonica type, called Chuchung. The scatterometer system consists of dual-polarimetric square horn antennas, HP8720D vector network analyzer (20MHz ${\sim}$ 20GHz), RF cables, and a personal computer that controls frequency, polarization and data storage. The scatterometer system is calibrated using a calibration kit (3.5mm, 85052D). The backscattering coefficients were calculated by applying radar equation for the measured at incidence angles between $20^{\circ}$ and $60^{\circ}$ for four polarization (HR, VV, HV, VH), respectively, and compared with rice growth data such as plant height, stem number, biomass, dry weight and LAI that were collected at time of each scatterometer measurement simultaneously.

• Journal of Magnetics
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• 제8권2호
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• pp.98-102
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• 2003

Microstructure and magnetic transport phenomina in rf sputtered AIN/CO type ten- layered discontinuous films of nanoscaled [AIN(3 nm)/Co(t nm)]…$_10$ with t$_Co$=1.0∼2.0 nm have been investigated. The microstructure and tunneling magnetic resistance of the samples are strongly dependent on the thickness of Co layer, Negative tunneling magneto-resistance due to the spin-dependent transport has been observed along the current-in-plane configuration in the samples having the Co layers below 1.6 nm thick. When the thickness of Co layer was less than 1.2 nm, randomly oriented granular Co particles were completely isolated and embedded in amorphous AIN matrix, and the films showed the superparamagnetic behavior with a high MR value of ${\Delta}p/p_0$=1.8%. As t$_Co$ increases, a transition from the regime of co-existence of superparamagnetic and ferromagnetic behaviors to ferromagnetic behavior was observed. funneling barrier called “decay length far tunneling” fur the films haying the thickness of Co layer from 1.4 to 1.6 nm was measured to be ranged from 0.004 to 0.021 ${\AA}$$^{-1}$.