• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.123-124
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• 2007

A silver indium sulfide ($AgInS_2$) epilayer was grown by the hot wall epitaxy method, which has not been reported in the liteniture. The grown $AgInS_2$ epilayer has found to be a chalcopyrite structure and evaluated to be high quality crystal. From the photocurrent measurement in the temperature range from 30 K to 300 K, the two peaks of A and B were only observed, whereas the three peaks of A, B, and C were seen in the PC spectrum of 10 K. These peaks are ascribed to the band-to-band transition. The valence band splitting of $AgInS_2$ was investigated by means of the photocurrent measurement. The temperature dependence of the energy band gap of the $AgInS_2$ obtained from the photocurrent spectrum was well described by the Varshni's relation, $E_g(T)=\;E_g(0)\;eV-(7.78\;{\times}\;10^{-4}\;eV/K)T^2/(T\;+\;116\;K\;K)$. Also, Eg(0) is the energy band gap at 0 K, which is estimated to be 2.036 eV at the valence band state A and 2.186 eV at the valence band state B.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.574-580
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• 2009

This study is investigate the bending behavior of real size RC beams strengthened with carbon fiber sheets. For experimental study, 1 control beam and 8 strengthened beams of real size(4 NU-beams and 4 U-beams) are tested and compared. NU-beam has not a V-shaped band and V-beam has a V-shaped band. The variables of experiment are composed of the number of carbon fiber sheets, the existence of U-shaped band, and four point loading, etc. The experimental results showed that the strengthening system with U-shaped band controls the premature debonding and provides a more ductile failure mode than the strengthening system without V-shaped band. It can be found from the load-deflection curves that as the number of fiber sheets is increased, the maximum strength and the flexural rigidity is increased. For the strengthening method with carbon fiber sheets of the real size RC beams, it is required the finding a solution to the bonding problem.

• Journal of the Korean Ceramic Society
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• v.41 no.5
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• pp.359-363
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• 2004

Photoluminescence excitation (PLE) spectroscopy studies were performed for anodically etched porous Zn, which exhibited a PL in the blue/violet spectral range peaking at 420 nm (2.95 eV), and oxidzed porous Zn at 380$^{\circ}C$ for 10 min and 12 h. A broad absorption band was observed at 4.07 eV (305 nm), 3.49 (355 nm) for anodically etched porous Zn. In contrast, both the oxidized porous Zn and sintered ZnO exhibited an almost identical one broad absorption band at 3.85 eV (322 nm), when PLE spectra were measured at 378 nm (3.28 eV). The oxidized porous Zn and sintered ZnO, which displayed both UV and green luminescence band, showed an additional absorption band at 389 nm (3.19 eV) and 467 nm (2.66 eV). In contrast, no significant absorption band was detected for a 10-min oxidized porous Zn, which only displayed one UV luminescence void of deep-level luminescence. These absorption bands determined by PLE studies enabled a clear understanding of an emission mechanism for the UV and green luminescence from ZnO.

• Transactions on Electrical and Electronic Materials
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• v.16 no.1
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• pp.5-9
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• 2015

Optical and electrical properties were studied for Antimony doped tin oxide thin films from precursors containing 10, 30, 50, and 70 atom% of Sb deposited on bare sodalime silica, barrier layer coated sodalime silica, and pure silica glass substrates by sol-gel spinning technique. The direct band gaps were found to vary from 3.13~4.12 eV when measured in the hv range of 2.5~5.0 eV, and varied from 4.22~5.08 eV when measured in the range of 4.0~7.0 eV. Indirect band gap values were in the range of 2.35~3.11 eV. Blue shift of band gap with respect to bulk band gap and Moss-Burstein shift were observed. Physical thickness of the films decreased with the increase in % Sb. Resistivity of the films deposited on SLS substrate was in the order of $10^{-2}$ ohm cm. Sheet resistance of the films deposited on barrier layer coated soda lime silica glass substrate was found to be relatively less.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.305-305
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• 2013

태양전지는 무기태양전지와 유기태양전지 등이 연구 되고 있는데 [1] 그 중 유기물질의 장점(높은 수율, solution phase processing, 저비용으로 전력 생산)과 무기재료의 장점(높은 전자 이동도, 넓은 흡수 범위, 우수한 환경 및 열 안정성)을 융합함으로써 장기적 구조안정성의 확보와 광전변환의 고 효율화를 동시에 달성하기 위한 유기무기 하이브리드 태양전지가 최근 큰 관심을 끌고 있다[2]. 본 연구에서는 hybrid photovoltaics에 유기물 MDMO-PPV와 전도성 고분자 PEDOT:PSS를 무기물 GaN 위에 spin coating 하여 두께에 다른 효율을 측정하였다. 유기물 MDMO-PPV는 p-형으로 클로로벤젠, 톨루엔과 같은 유기 용매에 잘 녹으며 HOMO 5.33eV, LUMO 2.97eV, energy band gap 2.4eV이며 99.5%의 순도 물질을 사용하였다. 또한 정공 수송층(hole transport layer, HTL)으로 PEDOT:PSS를 사용하였으며, HOMO 5.0eV, LUMO 3.6eV, energy band gap 1.4eV를 가지며 증류수나 에탄올과 같은 수용성 용매에 잘 녹는 특성을 가지고 있다. 무기물은 III-V 족 물질 n-GaN(002)을 사용하였고 valence band energy 1.9eV, conduction band energy 6.3eV, energy band gap 3.4eV, 높은 전자 이동도와 높은 포화 속도, 광전자 소자에 유리한 광 전기적 특성을 가지고 있다. 기판으로는 GaN와 격자 부정합도와 열팽창계수 부정합도가 큰 Sapphire (Al2O3) 이종 기판을 사용하였다. 전극으로 Au를 사용하였으며 E-beam증착하였다. Reflector로서 Al를 thermal evaporator로 증착하였다 [3]. 실험 과정은 두께에 따른 효율을 알아보기 위해 MDMO-PPV를 900~1,500 rpm으로 spin coating 하였고, 열처리에 따른 효율을 알아보기 위해 열처리 온도 조건을 $110{\sim}170^{\circ}C$의 변화를 주었다. FE-SEM으로 표면과 단면을 관찰하였으며 J-V 특성을 알아보기 위해 각 샘플마다 solar simulator를 사용하여 측정하였고 그 결과를 논의하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.347-351
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• 2003

A p-$CdIn_2Te_4$ single crystal has been grown by the Bridgman method without a seed crystal in a tree-stage vertical electric furnace. From photocurrent measurements, it was found that three peaks, A, B, and C, corresponded to an intrinsic transition due to the band-to-band transition from the valence band states ${\Gamma}_7(A),\;{\Gamma}_6(B),\;and\;{\Gamma}_7(C)$ to the conduction band state ${\Gamma}_6$, respectively. Also, the valence band splitting of the $CdIn_2Te_4$ crystal has been confirmed by photocurrent spectroscopy. The crystal field splitting and the spin orbit splitting were obtained to be 0.2360 and 0.1119 eV, respectively. Also, the temperature dependence of the band gap energy of the $CdIn_2Te_4$ crystal has been driven as the following equation of $E_g(T)\;=E_g(0)\;-\;(9.43\;{\times}\;10^{-3})T^2/(2676\;+\;T)$. In this equation, the Eg(0) was estimated to be 1.4750, 1.7110, and 1.8229 eV at the valence band state A, B, and C, respectively. The band gap energy of the p-$CdIn_2Te_4$ at room temperature was determined to be 1.2023 eV.

• Journal of electromagnetic engineering and science
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• v.16 no.4
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• pp.225-228
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• 2016

KRISS-V, a V-band millimeter-wave source module for a primary RF power standard and calibration system developed by the Korea Research Institute of Standards and Science is here presented. The output power of KRISS-V is several times higher than that of commercial amplifier/multiplier chains and is highly stable (the standard deviations of output power are less than 0.01% in the worst case). The spectral purity of KRISS-V is high enough to consider it a single-tone signal generator. We also added programmable attenuation capability to KRISS-V for remote power control. Moreover, the in-house source module is cost-effective and adaptable to various measurement schemes. The structure of the model as well as detailed component information are introduced so that it can be reproduced.

• Korean Journal of Materials Research
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• v.12 no.6
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• pp.431-435
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• 2002

The dark current and photocurrent(PC) spectrum of Mg-doped GaN thin film were investigated with various bias voltages and temperatures. At high temperature and small bias, the dark current is dominated by holes thermally activated from an acceptor level Al located at about 0.16 eV above the valence band maximum $(E_v)$, The PC peak originates from the electron transition from deep level A2 located at about 0.34 eV above the $E_v$ to the conduction band minimum $(E_ C)$. However, at a large bias voltage, holes thermally activated from A2 to Al experience the field-in-duces tunneling to form one-dimensional defect band at Al, which determines the dark current. The PC peak associated with the transition from Al to $E_ C$ is also observed at large bias voltages owing to the extended recombination lifetime of holes by the tunneling. In the near infrared region, a strong PC peak at 1.20 eV appears due to the hole transition from deep donor/acceptor level to the valence band.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.5C
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• pp.522-529
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• 2002

MMIC circuits in whole receiver system was fabricated based on GaAs pHEMT technology. And a V-band downconverter module was fabricated by integrating these circuits. The downconverter module consists of a LO drive power amplifier which generates 24dBm output power, a low noise amplifier(LNA) which shows 20 dB small signal gain, an active parallel feedback oscillator which generates 1.6 dBm output power, and a cascode mixer which shows over 6dB conversion gain. The good conversion gain performance of our mixer made no need to attach any IF amplifier which grows conversion gain. Measured results of the complete downconverter show a conversion gain of over 20 dB between 57.5 GHz and 61.7GHz without IF amplifier.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.767-770
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• 2003

A SiGe HBT MMIC differential VCO has been developed for C-band wireless LAN applications. The VCO produces -6.4 dBm output power at 4.75 GHz. The VCO exhibits a 490 MHz tuning range with control voltage from 0.5 V to 2.5 V. The phase noise of the VCO exhibits -106.5 dBc/Hz at 1 MHz offset from the 4.75 GHz carrier. The total current consumption of the VCO is 10 mA at a supply voltage of 3 V.