• 한국전기전자재료학회논문지
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• 제24권3호
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• pp.177-181
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• 2011

We have studied structural, optical, and electrical properties of the Al-doped ZnO (AZO) thin films being usable in transparent conducting oxides. The AZO thin films were deposited on the corning 1737 glass plate by the RF magnetron sputtering system. To find optimal properties of AZO for transparent conducting oxides, the RF power in sputtering process was varied as 40 W, 60 W, and 80 W, respectively. As RF power increased, the crystallinity of AZO thin film was decreased, the optical bandgap of AZO thin film increased. The transmittance of the film was over 80% in the visible light range regardless of the changes in RF power. The measurement of Hall effect characterizes the whole thin film as n-type, and the electrical property was improved with increasing RF power. The structural, optical, and electrical properties of the AZO thin films were affected by Al dopant content in AZO thin film.

• 산업기술연구
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• 제30권A호
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• pp.69-73
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• 2010

In this paper, we designed the RF-DC converter used in wireless power transmission system and studied how to design the RF-DC converter of high conversion efficiency. The RF-DC converter operate at 2.45GHz and the diode is connected with series. The RF-DC converter uses shorted stub for DC loop and matching. We can divide the RF-DC converter circuit into four blocks. The reflection coefficients between the blocks were optimized for the maximum conversion efficiency at 0 dBm input power and $1300{\Omega}$ load impedance. The final design of the RF-DC converter has a 52 percent conversion efficiency.

• 한국정보전자통신기술학회논문지
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• 제13권4호
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• pp.293-297
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• 2020

본 논문은 multiplex deposition sputter system을 이용하여 ITO 유리에 CdS 박막을 증착하여 태양전지에 적용될 수 있는 가장 좋은 조건을 찾고자 하였다. RF power를 50W, 100W, 150W로 변화주었고 스퍼터링시간은 10분으로 하였다. 투과율을 측정한 결과, 400~800 nm 영역에서 평균 투과율은 60%에서 80% 까지 측정되었으며 150W일 때 84%로 가장 좋은 특성이 측정되었다. 또한 밴드갭은 50W일 때 3.762eV, 100W일 때 4.037eV, 150W일 때 4.052eV로 측정되었다. XRD 분석에서는 RF power가 증가하여도 CdS의 구조인 Wurtzite(hexagonal)로 관찰되었다. 그리고 RF power가 증가할수록 입자가 크고 균일하게 증착 되었나, 100W 일 때 입자들이 조밀하게 구성되었고 밀도가 크다는 것을 알 수 있었다. 그리고 두께 측정 결과 RF power 가 증가할수록 균일성 있게 증가되었다.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2441-2446
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• 2018

This paper presents a radio frequency-to-direct current (RF-to-DC) converter for special RF power harvesting application at 915 MHz. The major featured components of the proposed RF-to-DC converter is the combination of a cross-coupled rectifier and an active diode: first, the cross-coupled rectifier boosts the input voltage to desired level, and an active diode blocks the reverse current, respectively. A prototype was implemented using $0.18{\mu}m$ CMOS technology, and the performance was proven from the fact that the targeted RF harvesting system's full-operation with higher power efficiency; even if the system's input power gets lower (e.g., from nominal 0 to min. -12 dBm), the proposed RF-to-DC converter constantly provides 1.47 V, which is exactly the voltage level to drive follow up system components like DC-to-DC converter and so on. And, maximum power conversion efficiency is 82 % calculated from the 0 dBm input power, 2.3 mA load current.

• 설비공학논문집
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• 제21권8호
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• pp.462-467
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• 2009

Researches and developments on BEMS are performed world-widely through sustainable management in various conditions. However, there are many obstacles to adapt the system in existing buildings because it needs highly expensive equipments, which are designed for newly built buildings, to install. Therefore, there are numerous limits exist when applying the BEMS in established buildings. The purpose of this study estimates the optimization of RF output power in WSN(Wireless Sensor Networks), which is the essential technology to develop PEMS. The results of this study is as follows ; 1) Applying WSN technique in buildings was possible. 2) As RF output power increases, the number of relay node reduced, therefore, the WSN showed more stability. 3) When estimating optimal RF output power in school, it should be considered between the number of relay node and RF output power. 4) Considering battery consumption and possibility of reception, the best suited RF output power is -20dbm in apartment house.

• 한국위성정보통신학회논문지
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• 제12권2호
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• pp.51-55
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• 2017

본 논문에서는 RF 에너지 하비스팅 네트워크에서 최대 전송 파워량 제한 및 최소 채널 용량 달성에 관한 제약조건을 만족시키며 에너지 하비스팅율과 채널 용량을 최대화 시키는 연구를 진행하였다. 전력 분할 기법 (power-splitting scheme) 기반 안테나로 구성된 주파수 분할 다중접속 환경에서 하나의 액세스 포인트 (access point)로부터 무선 에너지와 정보를 사용자들에게 동시에 송수신하는 모델을 가정하였다. 네트워크 성능 지표로서 에너지 효율 (energy efficiency)을 정의하고 이를 최대화 시킬 수 있는 Lagrange 이중 분해 기반의 최적화 솔루션을 제안하였다. 모의실험 결과를 통해 제안한 솔루션이 설정된 제한조건들을 만족하면서 효과적으로 에너지 효율을 최대화시키는 것을 확인하였다.

• 한국전기전자재료학회논문지
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• 제27권7호
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• pp.458-461
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• 2014

TiC thin films were deposited on Si wafer by unbalanced magnetron sputtering (UBMS) system with two targets of graphite and titanium. During the TiC sputtering, the RF power was varied from 100 W to 175 W and the physical and electrical properties of TiC films were investigated. The hardness and rms surface roughness of TiC films were improved with increasing RF power and the maximum hardness about 24 GPa and the minimum rms surface roughness about 1.2 nm were obtained. The resistivity of TiC films was decreased with increasing RF power. Consequently, the physical and electrical properties of TiC film wewe improved with increasing RF power.

• Transactions on Electrical and Electronic Materials
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• 제5권4호
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• pp.153-157
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• 2004

ITO thin films were deposited on PET and soda-lime glass substrates by a dc reactive magnetron sputtering of In-Sn alloy metal target without substrate heater and post-deposition thermal treatment. The dependency of rf-bias voltage and substrate power during deposition processing was investigated to control the electrical and optical properties of ITO films. The range of rf bias voltage is from 0 to -80 V and the substrate power is applied from 10 to 50 W. The minimum resistivity of ITO film is 5.4${\times}$10$^{-4}$ $\Omega$cm at 50 W power and rf-bias voltage of -20 V. The best transmittance of ITO films at 550 nm wavelength is 91 % in the substrate power of 30 W and rf-bias voltage of -80 V.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2014년도 추계학술대회 논문집
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• pp.254-255
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• 2014

RF magnetron sputtering법으로 증착한 비정질 IGZO 박막과 이를 Active layer로 이용한 TFT의 Transfer 특성에 대한 RF Power의 영향에 대해 연구하였다. Carrier concentration은 Sputtering 공정 중에 산소 분압으로 조절하였다. RF Power가 75에서 150W로 증가할수록 IGZO 박막의 Roughness는 12.2에서 $6.5{\AA}$ 감소하였고 Density는 6.0에서 $6.1g/cm^3$로 증가하였다. 또한, 모든 IGZO 박막은 가시광 영역에서 85% 이상의 투과율을 보였고 Optical band gap은 미세하게 감소하였다. RF Power가 증가할수록 a-IGZO TFT의 Threshold voltage는 0.9에서 7V로 증가하였고, Subthreshold slope은 0.3에서 0.8 V/decade로 증가하였다. 하지만 Mobility는 11에서 $19cm^2/V{\cdot}s$로 증가하였다.

• 한국전기전자재료학회논문지
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• 제21권4호
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• pp.296-299
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• 2008

The effects of radio frequency (RF) source power for decoupled plasma nitridation (DPN) process on the electrical properties and Fowler-Nordheim (FN) stress immunity of the oxynitride gate dielectrics for deep nano-technology devices has been investigated. With increase of RF source power, the threshold voltage (Vth) of a NMOS transistor(TR) decreased and that of a PMOS transistor increased, indicating that the increase of nitrogen incorporation in the oxynitride layer due to higher RF source power induced more positive fixed charges. The improved off-current characteristics and wafer uniformity of PMOS Vth were observed with higher RF source power. FN stress immunity, however, has been degenerated with increasing RF source power, which was attributed to the increased trap sites in the oxynitride layer. With the experimental results, we could optimize the DPN process minimizing the power consumption of a device and satisfying the gate oxide reliability.