• 대한전자공학회논문지TE
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• 제37권2호
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• pp.83-90
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• 2000

본 논문에서는 IMT2000 중계기용으로 1.88-1.98 ㎓ 대역 전력증폭기를 저 가격, 소형으로 개발하였다. 이 전력증폭기는 두 단으로 구성되어 있으며 초단은 P-HEMT (ATF-34143, 800 micron gate width, Agilent Technologies)를 사용하였으며, 종단은 GaAs FET(EFA240D-SOT89, 2400 micron gate width, Excelics Semiconductor)를 사용하였다. 개발된 전력 증폭기는 전체 주파수 대역인 1880-1980 ㎒에서 이득이 29.5㏈, 1㏈ gain compression point는 29.5dBm, 3rd order intercept point(OIP3)는 42dBm 그리고 입출력 return loss는 -10㏈/-l2㏈ 이다. 본 연구에서는 이 전력 증폭기를 설계하기 위하여 각 소자의 비선형 모델을 사용하여 전력증폭기의 여러 가지 비선형 특성을 설계할 수 있었으며, 이 전력 증폭기의 크기는 42(L) x 34(W) mm으로 소형화가 가능하였다.

• 미생물학회지
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• 제44권1호
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• pp.29-36
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• 2008

질소는 하수처리과정에서 제거되어야 하는 주요 오염물질 중의 하나이며, 세균 군집을 이용한 고도처리 시스템에서 생물학적 질소제거는 중요한 기술이다. 질산화반응은 생물학적 질소제거 시스템의 첫 단계로 미생물에 의해 진행된다. 암모니아는 암모니아산화세균에 의해 아질산염으로 산화되며, 그 후에 아질산염은 아질산염 산화세균에 의해 질산염으로 산화된다. 실험실 규모의 생물학적 질소제거 시스템인 변형된 eBAF 시스템, Nutrient removal laboratory 시스템과 반추기법을 적용한 rSBR 시스템의 질산화반응조 시료에서 16S rRNA 유전자를 이용한 terminal restriction fragment length polymorphism (T-RFLP) 방법으로 아질산염 산화세균군집을 분석하였다. 제한효소로 형성된 단편의 클러스터분석에서 Nitrobacter 군집은 각각의 폐수처리 시스템에 따라 군집의 차이가 있음이 나타났다. 그러나 Nitrospira 군집의 클러스터분석에서는 액체와 담체의 서식지 환경 차이에 의해 군집이 구분되었다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 1999년도 추계학술발표회 초록집
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• pp.56-56
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• 1999

For advanced TFT-LCD manufacturing processes, dry etching of thin-film layers(a-Si, $SiN_x$, SID & gate electrodes, ITO etc.) is increasingly preferred instead of conventional wet etching processes. To dry etch Al gate electrode which is advantageous for reducing propagation delay time of scan signals, high etch rate, slope angle control, and etch uniformity are required. For the Al gate electrode, some metals such as Ti and Nd are added in Al to prevent hillocks during post-annealing processes in addition to gaining low-resistivity($<10u{\Omega}{\cdot}cm$), high performance to heat tolerance and corrosion tolerance of Al thin films. In the case of AI-Nd alloy films, however, low etch rate and poor selectivity over photoresist are remained as a problem. In this study, to enhance the etch rates together with etch uniformity of AI-Nd alloys, magnetized inductively coupled plasma(MICP) have been used instead of conventional ICP and the effects of various magnets and processes conditions have been studied. MICP was consisted of fourteen pairs of permanent magnets arranged along the inside of chamber wall and also a Helmholtz type axial electromagnets was located outside the chamber. Gas combinations of $Cl_2,{\;}BCl_3$, and HBr were used with pressures between 5mTorr and 30mTorr, rf-bias voltages from -50Vto -200V, and inductive powers from 400W to 800W. In the case of $Cl_2/BCl_3$ plasma chemistry, the etch rate of AI-Nd films and etch selectivity over photoresist increased with $BCl_3$ rich etch chemistries for both with and without the magnets. The highest etch rate of $1,000{\AA}/min$, however, could be obtained with the magnets(both the multi-dipole magnets and the electromagnets). Under an optimized electromagnetic strength, etch uniformity of less than 5% also could be obtained under the above conditions.

• 한국통신학회논문지
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• 제24권12A호
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• pp.1932-1938
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• 1999

본 논문에서는 CDMA 전화기의 전력효율을 개선하고 소형화를 추구하기 위하여 기존의 듀플렉서를 여파기별로 분리한 후 평면형으로 구현하여 전력증폭기와 결합된 새로운 회로구조를 제안하였으며, 다층기판 상에 하나의 모듈로 제작하여 국내 PCS 전화기에 적용하였다. 제안된 구조의 이론적 타당성을 입증하기 위해 전체특성에 영향을 주는 핵심 변수를 중심으로 모의실험을 통해 중요한 성능들을 평가하였으며, 실험을 통해 성능개선을 확인하였다. 측정결과 결합모듈은 듀플렉서로서 역할을 다하였으며, 전력증폭기의 선형성을 나타내는 ACPR값은 IS-95 규격을 만족하였다. 또한 기존의 방식에 비해 제안된 구조는 전력증폭기 출력이 2dB이상 감소하여 상응하는 전류가 약 30mA 줄어들었고, power FET의 동작점을 B급으로 설정한 결과 실제 동작하는 환경에서 50mA의 전류를 절약할 수 있었다. 결합모듈의 총 부피는 1.08CC가 되어 지금까지 발표된 전력증폭기와 듀플렉서의 합보다 적다.

• 대한두경부종양학회지
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• 제3권1호
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• pp.107-114
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• 1987

Clinical application of hyperthermia using 8 MHz radiofrequency(capacitive type THERMOTRON RF-8) in cancer treatment was begun at Yonsei Cancer Center in 1985. From April 1985 to April 1986, 23 patients with loco-regionally advanced and persistent or recurrent carcinomas of the head and neck were treated with hyperthermia at the Department of Radiation Oncology, Yonsei University College of Medicine. Radiation therapy and/or chemotherapy were combined with hyperthermia to improve the tumor response. The response rate of 23 patients was 52%, 4 had complete response, and 7 had partial response. The factors affecting the tumor response were dose of irradiation(P=0.009). Complications related to treatment were found in 8 patients and all of them were self-limited. The result of this study indicates that localized hyperthermia as a combined modality has a significant role in palliation of advanced and recurrent head and neck cancer.

• 한국산학기술학회논문지
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• 제14권4호
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• pp.1883-1889
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• 2013

Fe-Si계 합금은 우주탐사용으로 응용되고 있는 Si-Ge합금보다는 낮은 성능지수를 나타내지만 원료가 풍부하여 저가이고, 제조가 간단하며, $800^{\circ}C$까지 사용가능한 중고온용 열전발전재료이다. 본 연구에서는 고주파 진공유도로를 이용해서 제조한 p형 $FeSi_2$의 열전물성에 미치는 입자크기 및 첨가물 영향에 대해 조사하였다. 조성입자크기가 작을수록 소결밀도 증가와 함께 입자와 입자간의 연결성 향상에 의해 도전율이 증가하였다. Seebeck 계수는 600~800K에서 최고값을 나타내었고, 잔존하는 ${\varepsilon}$-FeSi 금속전도상에 의해 약간 감소하였다. $Fe_2O_3$ 및 $Fe_3O_4$를 첨가한 경우, 잔존 금속전도상 및 Si 결핍양 증가에 의해 도전율은 증가하였고 Seebeck 계수는 감소하였다. 반면에 $SiO_2$를 첨가한 경우에는 도전율과 Seebeck 계수 모두 상승하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.159-159
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• 2011

Among the semiconductor ternary compounds in the I-III-$VI_2$ series, $CulnS_2$ ($CulnSe_2$) are one of the promising materials for photovoltaic applications because of the suitability of their electrical and optical properties. The $CuInS_2$ thin film is one of I-III-$VI_2$ type semiconductors, which crystallizes in the chalcopyrite structure. Its direct band gap of 1.5 eV, high absorption coefficient and environmental viewpoint that $CuInS_2$ does not contain any toxic constituents make it suitable for terrestrial photovoltaic applications. A variety of techniques have been applied to deposit $CuInS_2$ thin films, such as single/double source evaporation, coevaporation, rf sputtering, chemical vapor deposition and chemical spray pyrolysis. This is the first report that $CuInS_2$ thin films have been prepared by Aerosol Jet Deposition (AJD) technique which is a novel and attractive method because thin films with high deposition rate can be grown at very low cost. In this study, $CuInS_2$ thin films have been prepared by Aerosol Jet Deposition (AJD) method which employs a nozzle expansion. The mixed fluid is expanded through the nozzle into the chamber evacuated in a lower pressure to deposit $CuInS_2$ films on Mo coated glass substrate. In this AJD system, the characteristics of $CuInS_2$ films are dependent on various deposition parameters, such as compositional ratio of precursor solution, flow rate of carrier gas, stagnation pressure, substrate temperature, nozzle shape, nozzle size and chamber pressure, etc. In this report, $CuInS_2$ thin films are deposited using the deposition parameters such as the compositional ratio of the precursor solution and the substrate temperature. The deposited $CuInS_2$ thin films will be analyzed in terms of deposition rate, crystal structure, and optical properties.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.154-154
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• 2012

Flexible complementary inverters based on thin-film transistors (TFTs) are important because they have low power consumption and high voltage gain compared to single type circuits. We have manufactured flexible complementary inverters using pentacene and amorphous indium gallium zinc oxide (IGZO) for the p-channel and n-channel, respectively. The circuits were fabricated on polyimide (PI) substrate. Firstly, a thin poly-4-vinyl phenol (PVP) layer was spin coated on PI substrate to make a smooth surface with rms surface roughness of 0.3 nm, which was required to grow high quality IGZO layers. Then, Ni gate electrode was deposited on the PVP layer by e-beam evaporator. 400-nm-thick PVP and 20-nm-thick ALD Al2O3 dielectric was deposited in sequence as a double gate dielectric layer for high flexibility and low leakage current. Then, IGZO and pentacene semiconductor layers were deposited by rf sputter and thermal evaporator, respectively, using shadow masks. Finally, Al and Au source/drain electrodes of 70 nm were respectively deposited on each semiconductor layer using shadow masks by thermal evaporator. The characteristics of TFTs and inverters were evaluated at different bending radii. The applied strain led to change in voltage transfer characteristics of complementary inverters as well as source-drain saturation current, field effect mobility and threshold voltage of TFTs. The switching threshold voltage of fabricated inverters was decreased with increasing bending radius, which is related to change in parameters of TFTs. Throughout the bending experiments, relationship between circuit performance and TFT characteristics under mechanical deformation could be elucidated.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.479-479
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• 2011

Flexible inverters based on complementary thin-film transistor (CTFTs) are important because they have low power consumption and other advantages over single type TFT inverters. In addition, integrated CTFTs in flexible electronic circuits on low-cost, large area and mechanically flexible substrates have potentials in various applications such as radio-frequency identification tags (RFIDs), sensors, and backplanes for flexible displays. In this work, we introduce flexible complementary inverters using pentacene and amorphous indium gallium zinc oxide (IGZO) for the p-channel and n-channel, respectively. The CTFTs were fabricated on polyimide (PI) substrate. Firstly, a thin poly-4-vinyl phenol (PVP) layer was spin coated on PI substrate to make a smooth surface with rms surface roughness of 0.3 nm, which was required to grow high quality IGZO layers. Then, Ni gate electrode was deposited on the PVP layer by e-beam evaporator. 400-nm-thick PVP and 20-nm-thick ALD Al2O3 dielectric was deposited in sequence as a double gate dielectric layer for high flexibility and low leakage current. Then, IGZO and pentacene semiconductor layers were deposited by rf sputter and thermal evaporator, respectively, using shadow masks. Finally, Al and Au source/drain electrodes of 70 nm were respectively deposited on each semiconductor layer using shadow masks by thermal evaporator. Basic electrical characteristics of individual transistors and the whole CTFTs were measured by a semiconductor parameter analyzer (HP4145B, Agilent Technologies) at room temperature in the dark. Performance of those devices then was measured under static and dynamic mechanical deformation. Effects of cyclic bending were also examined. The voltage transfer characteristics (Vout- Vin) and voltage gain (-dVout/dVin) of flexible inverter circuit were analyzed and the effects of mechanical bending will be discussed in detail.

• Current Photovoltaic Research
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• 제6권1호
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• pp.21-26
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• 2018

Beside several advantages, the PV power generation as a clean energy source, is still below the supply level due to high power generation cost. Therefore, the interest in fabricating low-cost thin film solar cells is increasing continuously. $Cu_2O$, a low cost photovoltaic material, has a wide direct band gap of ~2.1 eV has along with the high theoretical energy conversion efficiency of about 20%. On the other hand, it has other benefits such as earth-abundance, low cost, non-toxic, high carrier mobility ($100cm^2/Vs$). In spite of these various advantages, the efficiency of $Cu_2O$ based solar cells is still significantly lower than the theoretical limit as reported in several literatures. One of the reasons behind the low efficiency of $Cu_2O$ solar cells can be the formation of CuO layer due to atmospheric surface oxidation of $Cu_2O$ absorber layer. In this work, atomic layer deposition method was used to remove the CuO layer that formed on $Cu_2O$ surface. First, $Cu_2O$ absorber layer was deposited by electrodeposition. On top of it buffer (ZnO) and TCO (AZO) layers were deposited by atomic layer deposition and rf-magnetron sputtering respectively. We fabricated the cells with a change in the deposition temperature of buffer layer ranging between $80^{\circ}C$ to $140^{\circ}C$. Finally, we compared the performance of fabricated solar cells, and studied the influence of buffer layer deposition temperature on $Cu_2O$ based solar cells by J-V and XPS measurements.