• Journal of information and communication convergence engineering
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• v.4 no.3
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• pp.105-107
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• 2006

Amorphous silicon is a kind of optical to electric conversion material with current or voltage type after generating a numerous free electron and hole when it is injected by light. It is very effective technology to make schottky diode by bonding thin film to use optical diode. In this paper, we have fabricated optical diode device by forming chrome silicide film through thermal processing with thin film($100{\AA}$) having optimal amorphous silicon. The optimal condition is that we make a thin film by using PECVD(Plasma Enhanced Chemical Vapor Deposition) to improve reliability and characteristics of optical diode. We have obtained high quality diode by using chrome silicide optical diode from dark current and optical current measurement compared to previous method. It makes a simple process and improves a good reliability.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.374-374
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• 2014

의료용 X-ray는 과거 analog 방식과, 연구가 진행 중이며 현재 많이 사용되고 있는 digital 방식으로 나누어진다. 최근, 광도전체와 형광체 기반의 flat panel X-ray detector의 발전에 따른 상용화가 이루어지고 있으며, 많은 발전 가능성이 제기되고 있다. flat panel X-ray detector 검출방식은 direct method (직접 방식)와 indirect method (간접 방식)로 나누어진다. 본 연구는 일반적으로 상용화 되어있는 amorphous seleinum (비정질 셀레늄)의 큰 일함수에 의한 저 해상력이라는 단점을 보완하기 위해, 작은 일함수를 가지는 물질을 사용하여, 영상을 얻을 시에 높은 해상력으로 표현할 수 있도록 하고, 원자번호가 높은 물질을 사용하여 X-ray 흡수율을 높일 수 있도록 기존 direct method에 많이 사용되고 있는 amorphous seleinum 기반 digital X-ray detector가 아닌, 이러한 장점을 충족시킬 수 있는 PbI2 물질 층을 사용하여 시편을 제작 하였다. PbI2를 같은 두께로 올린 후, 물질 층 상부에 Au 전극 면적을 다른 size로 제작한 시편으로 X-ray에 노출 시켰다. 이는 상부 전극 size 차이에 따른 신호 차이를 측정하여 전기적 특성을 평가하기 위한 것이다. 전도성을 띠고 있는 ITO (Indium - Tin - Oxide) glass를 이용하여 screen printing 방법으로 제작하였다. PbI2층을 약 160~180 um두께, $3cm{\times}3cm$ size로 5개 제작하였으며, 상부 전극으로는 Au를 진공 증착 시켰다. 상부 전극 size는 각각 시편 5개에 $0.5cm{\times}0.5cm$, $1cm{\times}1cm$, $1.5cm{\times}1.5cm$, $2cm{\times}2cm$, $2.5cm{\times}2.5cm$로 PbI2 물질 층 중앙에 증착 시켰다. 이러한 설정으로 X-ray 노출 시 관찰할 수 있는 PbI2의 전기적인 특성을 평가할 수 있었다. 관전압을 40 kVp, 60 kVp, 80 kVp, 100 kVp, 120 kVp, 140 kVp로 설정하고, 관전류는 100 mA로 설정하였으며, Dark current, Sensitivity를 측정하였다. Dark current와 Sensitivity를 측정한 뒤, 그 값을 이용하여 SNR (신호 대 잡음 비)값을 구해보았다.실험 결과 단위면적당 signal과 SNR을 분석할 수 있었다. 80 kVp로 기준을 잡고 결과 값을 보면 $0.5cm{\times}0.5cm$ 시편에서 2.92 nC/cm2, $2.5cm{\times}2.5cm$ 시편에서 0.84 nC/cm2로 상부 전극 크기가 작을수록 더 좋은 신호를 측정할 수 있었다. 똑같은 기준에서 SNR을 계산 해 보았을 때, $0.5cm{\times}0.5cm$ 시편에서 6.46, $2.5cm{\times}2.5cm$ 시편에서 1.91로 SNR역시 상부 전극 크기가 작을수록 더 큰 값을 확인할 수 있었다. 이러한 결과는 edge-effect의 영향으로 인해 나온 결과라고 할 수 있다. 이러한 실험 결과, detector 제작 시, 같은 물질을 사용하여 더 높은 효율을 내기 위해서는 큰 size의 상부 전극 보다는 작은 size의 상부 전극을 증착 시키는 것이 전기적 특성을 더욱 효율적으로 평가할 수 있을 것이라고 사료된다.

• Journal of the Korean Vacuum Society
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• v.19 no.3
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• pp.217-223
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• 2010

We grew multi-stacked InAs/$In_{0.1}Ga_{0.9}As$ DWELL (dot-in-a-well) structure by metal organic chemical vapor deposition and investigated optical properties by photoluminescence and I-V characteristics by dark current measurement. When stacking InAs quantum dots (QDs) with same growth parameter, the size and density of QDs were changed, resulting in the bimodal emission peak. By decreasing the flow rate of TMIn, we achieved the uniform multi-stacked QD structure which had the single emission peak and high PL intensity. As the growth temperature of n-type GaAs top contact layer (TCL) is above $600^{\circ}C$, the PL intensity severely decreased and dark current level increased. At bias of 0.5 V, the activation energy for temperature dependence of dark current decreased from 106 meV to 48 meV with increasing the growth temperature of n-type GaAs TCL from 580 to $650^{\circ}C$. This suggest that the thermal escape of bounded electrons and non-radiative transition become dominant due to the thermal inter-diffusion at the interface between InAs QDs and $In_{0.1}Ga_{0.9}As$ well layer.

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.196-200
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• 1989

The physical properties related to the GaInAs/InP crystal grown by LPE are discussed in terms of both the design and operation characteristics of the GaInAs/InP Pin photodiode has cutoff frequency of 358 MHz and responsivity, 0.53 A/W (λ=1.3${\mu}{\textrm}{m}$), with dark current density as low as 4$\times$10-4/$\textrm{cm}^2$ under reverse bias voltage of 5V.

• Korean Chemical Engineering Research
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• v.50 no.1
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• pp.72-75
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• 2012

In our experiments, strain-free nanowires(NWs) were dispersed on to the substrate, followed by e-beam lithography(EBL) to fabricate single nanowire ultraviolet(UV) sensor devices. Focused-ion beam(FIB), micro-Raman spectroscopy and photoluminescence were employed to characterize the structural and optical properties of AlGaN/GaN NWs. Also, I-V characteristics were obtained under both dark condition and UV lamp to demonstrate AlGaN/GaN NW-based UV sensors. The conductance of a single AlGaN/GaN UV sensor was 9.0 ${\mu}S$(under dark condition) and 9.5 ${\mu}S$ (under UV lamp), respectively. The currents were enhanced by excess carriers under UV lamp. Fast saturation and decay time were demonstrated by the cycled processes between UV lamp and dark condition. Therefore, we believe that AlGaN/GaN NWs have a great potential for UV sensor applications.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.32.2-32.2
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• 2013

We examine large-scale environmental effects on the formation and the mass growth of dark matter halos. To facilitate this, we constructed dark matter halo merger trees from a cosmological N-body simulation, which enabled us to trace the merger information and the assembly history of individual halos. In fact, since the massive halos are more likely to be distributed in denser regions than in less dense regions (Mo & White, 1996), the large-scale environment dependence of the properties of halos can be partly originated from the halo mass effect. In order to avoid such contamination, caused by the mass dependence of halo properties, we carefully measured the local overdensity as the indicator of large-scale environment, which was calculated to be as independent of halo mass as possible. Small halos (${\sim}10^{11-12}M_{\odot}$), which usually host isolated single galaxies, show a notable difference on the formation time of galaxies depending on their large-scale environments, which reconfirms halo assembly bias (Gao & White, 2007). Furthermore, we investigate how this environmental effect on small halos is correlated with the mass assembly history of galaxies by using our semi-analytic model. We found that assembly bias in small halos does not have significant effects on the formation time or on the star formation history of galaxies residing in those halos except for the individual stellar mass of galaxies at z = 0. On average, isolated galaxies in high-density regions tend to be slightly more massive than those in low-density regions. Although the observational data from the current galaxy surveys is not yet sufficient for testing this prediction, future galaxy surveys will be able to explore these small galaxies more thoroughly.

• Journal of Radiation Industry
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• v.9 no.1
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• pp.1-7
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• 2015

The trend of x-ray image sensor has been evolved from an amorphous silicon sensor to a crystal silicon sensor. A crystal silicon X-ray sensor, meaning a X-ray CIS (CMOS image sensor), is consisted of three transistors (Trs), i.e., a Reset Transistor, a Source Follower and a Select Transistor, and a photodiode. They are highly sensitive to radiation exposure. As the frequency of exposure to radiation increases, the quality of the imaging device dramatically decreases. The most well known effects of a X-ray CIS due to the radiation damage are increments in the reset voltage and dark currents. In this study, a pixel array of a X-ray CIS was made of $20{\times}20pixels$ and this pixel array was exposed to a high radiation dose. The radiation source was Co-60 and the total radiation dose was increased from 1 to 9 kGy with a step of 1 kGy. We irradiated the small pixel array to get the increments data of the reset voltage and the dark currents. Also, we simulated the radiation effects of the pixel by MCNP (Monte Carlo N-Particle) simulation. From the comparison of actual data and simulation data, the most affected location could be determined and the cause of the increments of the reset voltage and dark current could be found.

• 한국태양에너지학회:학술대회논문집
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• 2009.11a
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• pp.98-103
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• 2009

In this paper, we test the electrical resistance of flat wire in the PV module. normally solar cell has two kind of flat wire(inter connection ribbon and bus bar ribbon). we found the phenomenon that has a unbalance with resistance when we make a wiling between of string. So, we measurement the resistance of flat wire each other. and analysis of missmatch with resistance between flat wires on PV module. next to survey of IR picture on missmatch flat wire samples for analyze of missmatch with current in the wire. and we perform IR test with solar cell that has a connection with flat wire for test the effect of missmatch resistance on solar cell. Finally we perform the Dark I-V test for survey of effect by the unbalance of resistance. By the result of Dark I-V test, the series resistance of existing connection sample is large more then innovated connection sample.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.35.2-35.2
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• 2018

Using the K-band Multi-object Spectrograph (KMOS) at the Very Large Telescope (VLT), the KMOS Redshift One Spectroscopic Survey (KROSS) has gathered integral-field data for ~800 star-forming galaxies at a redshift z~1, when the universe was roughly half its current age and forming the bulk of its stars. With spatially-resolved observations, KROSS reveals galaxies that are both gas-rich and highly turbulent. It is possible to derive the observed and baryonic Tully-Fisher (luminosity - rotation velocity) relations, thus constraining the mass-to-light ratios and total (luminous + dark) masses of the galaxies. This in turn highlights the dependence of the relation zero-point on the degree of rotational support of the galaxies (rotational velocity to velocity dispersion ratio). By degrading and analogously analysing integral-field data of hundreds of local galaxies from the Sydney-AAO Multi-object Integral-field Spectrograph (SAMI) survey, a robust comparison z=0 Tully-Fisher relation can also be derived, thus further constraining the luminous and dark mass growth of disk galaxies over the last 7 billions years. This unique comparison also reveals that systematic effects associated with sample selection and analysis methods are as large as the effects expected from cosmological evolution, and thus that most other comparisons employing heterogeneous data and/or methods can safely be ignored.

• The Journal of Information Systems
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• v.32 no.2
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• pp.137-152
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• 2023

Purpose The purpose of this study is to analyze big data related to DURIBAL from the operation of taxis reserved for the disabled to identify the issues and suggest solutions. ESG management should be translated into "environmental factors, social responsibilities, and transparent management." Therefore, the current study used Big Data analysis to analyze the factors affecting the standby of taxis reserved for the disabled and relevant problems for implications on convenience of social weak. Design/methodology/approach The analysis method used R, Excel, Power BI, QGIS, and SPSS. We proposed several suggestions included problems with managing cancellation data, minimization of dark data, needs to develop an integrated database for scattered data, and system upgrades for additional analysis. Findings The results showed that the total duration of standby was 34 minutes 29 seconds. The reasons for cancellation data were mostly use of other modes of transportation or delayed arrival. The study suggests development of an integrated database for scattered data. Finally, follow-up studies may discuss government-initiated big data analysis to comparatively analyze the use of taxis reserved for the disabled nationwide for new social value.