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Hot wall epitaxy(HWE)법에 의한 $AgGaS_2$ 단결정 박막 성장과 열처리 효과
문종대,Moon Jongdae 한국결정성장학회 2005 韓國結晶成長學會誌 Vol.15 No.1
AgGaS₂ 단결정 박막을 수평 전기로에서 합성한 AgGaS₂ 다결정을 증발원으로하여, hot wall epitaxy(HWE) 방법으로 증발원과 기판(반절연성-GaAs(100))의 온도를 각각 590℃, 440℃로 고정하여 성장하였다. 이때 단결정 박막의 결정성은 광발광 스펙트럼과 이중결정 X-선 요동곡선(DCRC)으로 부터 구하였다. AgGaS₂의 광흡수 스펙트럼으로부터 구한 온도에 의존하는 에너지 밴드갭 E/sub g/(T)는 Varshni 공식에 fitting한 결과 E/sub g/(T) = 2.7284 eV - (8.695×10/sup -4/ eV/K)T²/(T + 332 K)를 잘 만족하였다. 성장된 AgGaS₂ 단결정 박막을 Ag, Ga, S 분위기에서 각각 열처리하여 10K에서 photoluminescience(PL) spectrum을 측정하여 점 결함의 기원을 알아보았다. PL 측정으로 부터 얻어진 V/sub Ag/, V/sub s/, Ag/sub int/, 그리고 S/sub int/는 주개와 받개로 분류되어졌다. AgGaS₂ 단결정 박막을 Ag 분위기에서 열처리하면 n형으로 변환됨을 알 수 있었다. 또한, Ga 분위기에서 열처리하면 열처리 이전의 PL 스펙트럼을 보이고 있어서. AgGaS₂ 단결정 박막에서 Ga은 안정된 결합의 형태로 있기 때문에 자연 결함의 형성에는 관련이 없음을 알았다. A stoichiometric mixture of evaporating materials for AgGaS₂ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, AgGaS₂ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the hot wall epitaxy (HWE) system. The source and substrate temperatures were 590℃ and 440℃, respectively. The temperature dependence of the energy band gap of the AgGaS₂ obtained from the absorption spectra was well described by the Varshni's relation, E/sub g/(T) = 2.7284 eV - (8.695×10/sup -4/ eV/K)T²/(T + 332 K). After the as-grown AgGaS₂ single crystal thin films was annealed in Ag-, S-, and Ga-atmospheres, the origin of point defects of AgGaS₂ single crystal thin films has been investigated by the photoluminescence (PL) at 10 K. The native defects of V/sub Ag/, V/sub s/, Ag/sub int/, and S/sub int/ obtained by PL measurements were classified as a donors or accepters type. And we concluded that the heat-treatment in the Ag-atmosphere converted AgGaS₂ single crystal thin films to an optical n-type. Also, we confirmed that Ga in AgGaS₂/GaAs crystal thin films did not form the native defects because Ga in AgGaS₂ single crystal thin films existed in the form of stable bonds.
A New Strained-Si Channel High Voltage MOSFET for High Performance Power Applications
Young-Kyun Cho,Tae Moon Roh,Jongdae Kim 한국전자통신연구원 2006 ETRI Journal Vol.28 No.2
We propose a novel power metal oxide semiconductor field effect transistor (MOSFET) employing a strained-Si channel structure to improve the current drivability and on-resistance characteristic of the high-voltage MOSFET. A 20 nm thick strained-Si low field channel NMOSFET with a 0.75 μm thick Si0.8Ge0.2 buffer layer improved the drive current by 20% with a 25% reduction in on-resistance compared with a conventional Si channel high-voltage NMOSFET, while suppressing the breakdown voltage and subthreshold slope characteristic degradation by 6% and 8%, respectively. Also, the strained-Si high-voltage NMOSFET improved the transconductance by 28% and 52% at the linear and saturation regimes.
Yil Suk Yang,Tae Moon Roh,Soon il Yeo,Woo H. Kwon,Jongdae Kim 대한전자공학회 2009 Journal of semiconductor technology and science Vol.9 No.1
This paper describes design of high energy efficiency 32 bit parallel processor core using instructtion-levels data gating and dynamic voltage scaling (DVS) techniques. We present instruction-levels data gating technique. We can control activation and switching activity of the function units in the proposed data technique. We present instruction-levels DVS technique without using DC-DC converter and voltage scheduler controlled by the operation system. We can control powers of the function units in the proposed DVS technique. The proposed instruction-levels DVS technique has the simple architecture than complicated DVS which is DC-DC converter and voltage scheduler controlled by the operation system and a hardware implementation is very easy. But, the energy efficiency of the proposed instruction-levels DVS technique having dual-power supply is similar to the complicated DVS which is DC-DC converter and voltage scheduler controlled by the operation system. We simulate the circuit simulation for running test program using Spectra. We selected reduced power supply to 0.667 times of the supplied power supply. The energy efficiency of the proposed 32 bit parallel processor core using instruction-levels data gating and DVS techniques can improve about 88.4% than that of the 32 bit parallel processor core without using those. The designed high energy efficiency 32 bit parallel processor core can utilize as the coprocessor processing massive data at high speed.
Yil Suk Yang,Woo H. Kwon,Tae Moon Roh,Soon il Yeo,Jongdae Kim 대한전자공학회 2009 Journal of semiconductor technology and science Vol.8 No.1
Abstract—This paper describes design of high energy efficiency 32 bit parallel processor core using instructtion- levels data gating and dynamic voltage scaling (DVS) techniques. We present instruction-levels data gating technique. We can control activation and switching activity of the function units in the proposed data technique. We present instruction-levels DVS technique without using DC-DC converter and voltage scheduler controlled by the operation system. We can control powers of the function units in the proposed DVS technique. The proposed instruction-levels DVS technique has the simple architecture than complicated DVS which is DC-DC converter and voltage scheduler controlled by the operation system and a hardware implementation is very easy. But, the energy efficiency of the proposed instruction-levels DVS technique having dual-power supply is similar to the complicated DVS which is DC-DC converter and voltage scheduler controlled by the operation system. We simulate the circuit simulation for running test program using Spectra. We selected reduced power supply to 0.667 times of the supplied power supply. The energy efficiency of the proposed 32 bit parallel processor core using instruction-levels data gating and DVS techniques can improve about 88.4% than that of the 32 bit parallel processor core without using those. The designed high energy efficiency 32 bit parallel processor core can utilize as the coprocessor processing massive data at high speed.
Durability Improvement of Solid Electrolyte CO2 Sensor Against Humidity Variations.
Lee, Hyung-Kun,Choi, Nak-Jin,Moon, Seung Eon,Heo, Jin Ah,Yang, Woo Seok,Kim, Jongdae American Scientific Publishers 2015 Journal of Nanoscience and Nanotechnology Vol.15 No.1
<P>The sensing materials of potentiometric CO2 sensors utilize alkali/alkali-earth metal carbonates or their combinations. However, lithium carbonate easily responds to humidity resulting in incorrect information regarding CO2 concentration. Herein, the authors report a new sensing material combination (Li2CO3/BaCO3/LiOH/Ba(OH)2 (1:2:0.05:0.1 molar ratio)) for a potentiometric CO2 sensor that is not affected by humidity. The electromotive force (EMF) of the sensor using a combination of Li2CO3, BaCO3, LiOH, and Ba(OH)2 drifted by 1.5% when the relative humidity was changed from 25% to 70%, which is superior to a drift of 6% of a sensor using Li2CO3 and BaCO3, as this sensing material is known to be robust to changes in humidity.</P>
양우석(Woo Seok Yang),문승언(Seung Eon Moon),이재우(Jaewoo Lee),김종대(Jongdae Kim) 대한전자공학회 2010 대한전자공학회 학술대회 Vol.2010 No.6
Microsensors have been developing by technology convergence of semiconductor, MEMS and nano. MEMS microphone, iMEMS infrared image sensor and nano-MEMS gas sensor are currently prominent in industries. So, we are summarized their technology development trend and R&D results in ETRI.
Uk-won Nam,Won-kee Park,Junga Hwang,Jongdae Sohn,Bongkon Moon,Sunghwan Kim 한국우주과학회 2020 Journal of Astronomy and Space Sciences Vol.37 No.4
We develop the tissue-equivalent proportional counter (TEPC) type’s space radiation dosimeter to measure in-situ aviation radiation. That was originally developed as a payload of small satellite in the low-earth orbit. This dosimeter is based on a TEPC. It is made of an A-150 tissue-equivalent plastic shell of an internal diameter of 6 cm and a thickness of 0.3 cm. TEPC is filled with pure propane at 13.9 torrs to simulate a cell diameter of 2 μm. And the associated portable and low power electronics are also implemented. The verification experiments have been performed by the calibration experiments at ground level and compared with Liulin observation at aircraft altitude during the flight between Incheon airport (ICN) and John F. Kennedy airport (JFK). We found that the TEPC dosimeter can be used as a monitor for space radiation dosimeter at aviation altitude based on the verification with Liulin observation.