• 한국진공학회지
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• 제18권5호
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• pp.352-357
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• 2009

본 연구에서는 1.1 eV의 에너지대역을 흡수할 수 있는 InAs 양자점구조와 1.3 eV의 에너지 대역을 흡수 할 수 있는 InGaAs 양자우물구조를 이용한 텐덤형 태양전지의 구조를 1D poisson을 이용해 설계하고, 분자선 에피택시 장비를 이용하여 각각 5, 10, 15층씩 쌓은 양자점 및 양자우물구조를 삽입하여 p-n접합을 성장하였다. Photoluminescence (PL) 측정을 이용한 광학적특성 평가에서 양자점 5층 및 양자우물 10층을 삽입한 구조의 PL 피크가 가장 높은 상대발광강도를 나타냈으며, 각각 1.1 eV 및 1.3 eV에서 57.6 meV 및 12.37 meV의 Full Width at Half Maximum을 나타내었다. 양자점의 밀도 및 크기는 Reflection High-Energy Electron Diffraction system과 Atomic Force Microscope를 이용해 분석하였다. 그리고 GaAs/AlGaAs층을 이용한 터널접합에서는 I-V 측정을 통하여 GaAs층의 두께(20, 30, 50 nm)에 따른 터널링 효과를 평가하였다. GaAs 층의 두께가 30 nm 및 50 nm의 터널접합에서는 backward diode 특성을 나타낸 반면, 20 nm GaAs층의 GaAs/AlGaAs 터널접합에서는 다이오드 특성 곡선을 확인하였다.

• 한국재료학회지
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• 제19권3호
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• pp.163-168
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• 2009

$Eu^{3+}$-doped $Y_2O_3$ red phosphor was synthesized in a flux method using the chemicals $Y_2O_3,\;Eu_2O_3,\;H_3BO_3$ and $BaCl_2{\cdot}2H_2O$. The effect of a flux addition on the preparation of $Y_2O_3:Eu_{3+}$ red phosphor used as a cold cathode fluorescence lamp was investigated. $H_3BO_3$ and $BaCl_2{\cdot}2H_2O$ fluxes were used due to their different melting points. The crystallinity, thermal properties, morphology, and emission characteristics were measured using XRD, TG-DTA, SEM, and a photo-excited spectrometer. Under UV excitation of 254 nm, $Eu_2O_3$ 3.7 mol% doped $Y_2O_3$ exhibited a strong narrow-band red emission, peaking at 612 nm. From this result, the phosphor synthesized by firing $Y_2O_3$ with 3.7 mol% of $Eu_2O_3$, 0.25 mol% of $H_3BO_3$ and 0.5 mol% of $BaCl_2{\cdot}2H_2O$ fluxes at $1400^{\circ}C$ for 2 hours had a larger particle size of $4{\mu}m$ on average compared to the phosphor of the $H_3BO_3$ flux alone. In addition, a phosphor synthesized by the two fluxes together had a rounder corner shape, which led to the maximum emission intensity.

• 방사선산업학회지
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• 제6권4호
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• pp.305-310
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• 2012

This study examined radiation detection properties of imported perilla seeds, almonds, and soybeans. Food samples were irradiated at doses of 0.5, 1, 2, and 4 kGy and analyzed by photo-stimulated luminescence (PSL), thermoluminescence (TL), and electron spin resonance (ESR). The results of PSL showed that photon counts of irradiated perilla seeds and soybeans were $32,959counts{\cdot}60sec^{-1}$ and $7,234counts{\cdot}60sec^{-1}$, respectively, at an irradiation dose of 0.5 kGy, and the photon count of irradiated almonds was $5,581counts{\cdot}60sec^{-1}$ at an irradiation dose of 1 kGy. The results of TL showed that this technique is useful for detecting irradiated samples; the TL ratios ($TL_1/TL_2$) measured for the food samples at an irradiation dose of 0.5 kGy were 0.2301 for perilla seeds, 0.4595 for almonds, and 0.4827 for soy beans. Lastly, results of ESR spectroscopy for only soybeans revealed specific signals derived from free radicals captured in the cellulose. In conclusion, PSL, TL, and ESR methods can be used for the detection of gamma-irradiated soybean samples, whereas gamma-irradiated perilla seeds and almonds can be confirmed by a serial detection with a TL method after PSL.