• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권1호
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• pp.12-17
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• 1999

$MgIn_2Se_4 and MgIn_2Se_4 : Ni^{2+}$ single crystals were grown in the rhombohedral structure by the chemical transport reaction (C.T.R.) method using iodine as a transport agent. The optical absorption measured near the fundamental band edge showed that the optical energy band structure of these compounds had a direct band gap. The fundamental absorption band edge of these single crystals shift to a shorter wavelength region by decreasing temperature and the temperature dependence of the optical energy gaps in these compounds satisfy Varshni equation. The impurity optical absorption peaks due to nickel are observed in $MgIn_2Se_4 and MgIn_2Se_4 : Ni^{2+}$ single crystal. These impurity optical absorption peaks can be attributed to the electronic transitions between the split energy levels of $Ni_{2+}$ ions located at $T_d$ symmetry site of $MgIn_2Se_4$ host lattice. In the hotoluminescence spectrum of the single crystal at 10 K, a blue emission with a peak at 687nm and a green emission with a peak at 815nm for the $MgIn_2Se_4$ single crystal were observed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.179-180
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• 2007

Single crystal $AgGaSe_2$ layers were grown on thoroughly etched semi-insulating GaAs(100) substrate at $420^{\circ}C$ with hot wall epitaxy (HWE) system by evaporating $AgGaSe_2$ source at $630^{\circ}C$. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of single crystal $AgGaSe_2$ thin films measured with Hall effect by van der Pauw method are $4.05{\times}\;10^{16}/cm^3$, $139\;cm^2/V{\cdot}s$ at 293 K. respectively. The temperature dependence of the energy band gap of the $AgGaSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=1.9501\;eV\;-\;(8.79{\times}10^{-4}\;eV/K)T^2$/(T + 250 K). The crystal field and the spin-orbit splitting energies for the valence band of the $AgGaSe_2$ have been estimated to be 0.3132 eV and 0.3725 eV at 10 K, respectively, by means of the phcitocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}So$ definitely exists in the $\Gamma_5$ states of the valence band of the $AgGaSe_2$. The three photocurrent peaks observed at 10 K are ascribed to the $A_1$-, $B_1$-, and $C_1$-exciton peaks for n = 1.

• 한국수소및신에너지학회논문집
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• 제22권3호
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• pp.349-356
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• 2011

During the process of synthesis of $TiO_2$ powders using a high-speed planetary milling machine, Fe metallic powders were created which could be dissolved in sulfuric acid solution. With adding $NH_4OH$ solution to the $TiO_2$ powder, it was found that the crystal structure of the synthesized powder did not change and the crystal size decreased slightly. However, when the sulfur powder is mixed with $TiO_2$, the crystal structure of the MA powder was changed from anatase into rutile phase and its size decreased significantly which is in the order of nm in diameter. In case of mechanical alloying with $TiO_2$ powder only, the crystal structure of the powder was transformed into rutile phase and its size was greatly reduced into several nm. Because its size becomes fine, the energy band gap of its rutile phase is larger than that of bulk states (3.0eV).

• 한국수소및신에너지학회논문집
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• 제5권1호
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• pp.41-49
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• 1994

Ti-Bi alloy was prepared by arc melting of appropriate amounts of titanium and bismuth powder. The photocurrent($I_{ph}$) of Ti-Bi oxide electrode was increased with the increase of Bi content, up to 10wt%. The maximum $I_{ph}$ showed $7.6mA/cm^2$ at V=0.5V vs. SCE. The band gap energy of Ti-Bi oxide electrode was observed to 3.0~2.87eV. Surface barrier($V_s$) of Ti-10Bi oxide electrode showed maximum value(1.08V) but didn't exceed 1.23V, then it was impossible to run $H_2$ generation without any other energy sources other than the light. Ti-Bi oxide electrode was found to be quite stable under alkaline solution and showed no signs of photodecomposition.

• 센서학회지
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• 제1권2호
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• pp.165-172
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• 1992

3가와 5가 이온의 첨가가 전기전도도 및 감응도에 어떤 영향을 미치는가를 확인하기 위하여, In와 Sb를 Tin Oxide에 공침법으로 첨가하였다. Sb는 5가 이온으로 cassiterite 구조에 들어가서 열에너지에 의하여 이들 이온을 여기시켜 전도대로 밀어올리리라고 여겨진다. In 이온은 결정격자 속에 $In^{3+}$로 들어가서 원자가대로 부터 전자를 받게 되고 그러므로써 1가나 2가가 되리라 생각한다. 그러나, 이러한 현상들이 $SnO_{2}$에 존재하는 전위장벽을 2종의 이온첨가에 의하여 일어나는 resistivity에 끼치는 영향과 비교해 볼 때 감응도에는 어떤 영향을 보이는지 고찰하였다.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.3122-3125
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• 2021

Electromagnetic vortex flowmeter is a new type of instrument for detecting leakage of steam generator, and the signal processing method based on the envelope to calculate energy ratio can effectively detect bubbles in sodium flow. The signal processing method is not affected by changes in the amplitude of the sensor output signal, which is caused by changes in magnetic field strength and other factors. However, the detection sensitivity of the electromagnetic vortex flowmeter is reduced. To this end, a signal processing method based on inverse Fourier transform to calculate energy ratio is proposed. According to the difference between the frequency band of the bubble noise signal and the flow signal, only the amplitude in the frequency band of the flow signal is retained in the frequency domain, and then the flow signal is obtained by the inverse Fourier transform method, thereby calculating the energy ratio. Using this method to process the experimental data, the results show that it can detect 0.1 g/s leak rate of water in the steam generator, and its performance is significantly better than that of the signal processing method based on the envelope to calculate energy ratio.

• 대한전자공학회논문지TC
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• 제47권8호
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• pp.42-46
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• 2010

에너지 검파 형태의 스펙트럼 감지는 수신 신호의 에너지를 검파 임계값과 비교하여 1차 사용자(primary user)의 활동 여부를 탐지한다. 그런데 이때 임계값은 달성하고자 하는 오류 경보 확률 및 잡음의 에너지 수준과 밀접한 관련을 갖는다. 따라서 만약 잡음의 에너지 수준이 변한다면 임계값도 조정되어야 한다. 현재까지 발표된 에너지 검파에 대한 연구들은 대부분 잡음의 에너지 수준을 이미 알고 있다는 것을 전제로 한 것이었다. 본 논문에서는 잡음의 백색성을 전제로 하여 임계값을 조절하는 방안을 제안하고, 그에 따른 검파 성능 분석 결과를 제시하고자 한다. 분석 결과, 제안한 방식은 잡음 에너지 수준과는 상관없이 일정한 오류 경보 확률을 달성할 수 있으며, 잡음 에너지를 추정하는데 사용되는 신호의 대역폭과 에너지 측정 기간의 곱이 커질수록 스펙트럼 감지 성능이 향상됨을 확인할 수 있었다.

• 방사성폐기물학회지
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• 제11권3호
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• pp.245-251
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• 2013

NaI(Tl) 섬광검출기로 측정한 에너지 스펙트럼으로부터 공간 감마 선량률을 계산하기 위하여 에너지밴드 방법과 G-factor 방법의 결과를 비교 검토하였다. 먼저 한국원자력연구원 내 운영 중인 환경방사선감시기 EFRD 3300에 장착된 3"${\Phi}X3$" NaI(Tl) 검출기의 G-factor를 MCNP 모델링을 통하여 입사 방사선의 방향에 따라 각각 구하였으며, 이로부터 계산된 선량률과 에너지밴드 방법으로 계산된 결과의 차이를 비교 검토함으로써 EFRD 3300에 적용 가능한 최적의 G-factor 값을 유도하였다. 그리고 EFRD 3300 방사선감시기가 운영되고 있는 지역 주변에 위치한 HPIC 방사선감시기의 선량률과 비교 검토를 수행하였으며, 3"${\Phi}X3$" NaI(Tl) 검출기 기반의 EFRD 3300에서 $7.7{\mu}R/h$의 측정값을 얻어 약 $3{\mu}R/h$ 정도의 차이를 보였다. 일반적으로 HPIC 방사선감시기는 고에너지 우주방사선량도 측정할 수 있는 것으로 알려져 있으므로, 이 차이는 3"${\Phi}X3$" NaI 계측기로 측정되지 못하는 고에너지 영역의 우주방사선에 의한 영향으로 평가할 수 있었다.

• 전자공학회논문지A
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• 제29A권9호
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• pp.56-64
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• 1992

Because of a small bandgap energy, a high doping density, and a low operating temperature, the dark current in HgCdTe photodiode is almost composed of a tunneling current. The tunneling current is devided into an indirect tunneling current via traps and a band-to-band direct tunneling current. The indirect tunneling current dominates the dark current for a relatively high temperature and a low reverse bias and forward bias. For a low temperature and a high reverse bias the direct tunneling current dominates. In this paper, to verify the tunneling currents in HgCdTe photodiode, the new tunneling-recombination equation via trap is introduced and tunneling-recombination current is calculated. The new tunneling-recombination equation via trap have the same form as SRH (Shockley-Read-Hall) generation-recombination equation and the tunneling effect is included in recombination times in this equation. Chakrabory and Biswas's equation being introduced, band to band direct tunneling current are calculated. By using these equations, HgCdTe (mole fraction, 0.29 and 0.222) photodiodes are analyzed. Then the temperature dependence of the tunneling-recombination current via trap and band to band direct tunneling current are shown and it can be known what is dominant current according to the applied bias at athe special temperature.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.115.1-115.1
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• 2011

최근 기본적인 pin 구조의 박막 cell 에서 i layer를 최적화 시키는 방안으로 double layer 구조가 많이 연구되고 있다. 본 연구에서는 ASA(Advanced Semicon ductor Analysis) simulation을 이용하여 i-double layer 최적화에 대한 연구를 진행해 보았다. 두께 150/150nm의 i double layer의 band gap 가변을 한 simulation 결과를 보았을 때, p쪽의 band gap이 상승하면서 intrinsic layer 내의 field가 증가하여 recombination center가 감소하였으나 FF의 감소가 있었다. n쪽의 band gap을 상승 시켰을때 n/i 쪽 field 증가로 Voc가 상승되어 초기 효율이 증가하였으나 intrinsic layer내의 field가 감소하여 recombination center가 오히려 증가하였다. 결과적으로 electric field와 효율을 동시에 고려했을 때 두께 300nm, 1.75의 band gap을 가지는 single layer 보다 150/150nm두께에 1.8/1.7 또는 1.8/1.75의 bandgap을 가지는 double layer를 사용하였을 때 보다 높은 효율을 얻을 수 있었다.