• Journal of Radiation Protection and Research
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• v.2 no.1
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• pp.17-23
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• 1977

The neutron dosimetrical parameters, i. e., the fission neutron spectrum-averaged cross-sections and the fluence-to-dose conversion factors have been calculated for some threshold detectors with the aid of a computer. The threshold detectors under investigation were the $^{115}In(n,\;n')^{115m}In,\;^{32}S(n,\;p)^{32}P$ and $^{27}Al(n,\;{\alpha})^{24}Na$ reactions. It is revealed that the average cross-sections($\bar{\sigma}$) for the $^{32}S(n,\;p)^{32}P$ reaction are independent of the spectral functions, namely, the Watt-Cranberg and Maxwellian forms. In the case of the $^{27}Al(n,\;{\alpha})^{24}Na$ reaction a variation of the $\bar{\sigma}$ values appears to be highly dependent on the fissioning types. It seems that both the average cross-section for the $^{115}In(n,\;n')^{11m}In$ reaction and the conversion factor are insensitive to the spectral deformation of fission neutrons. These phenomena make it applicable to use indium as a possible integral fast neutron dosimeter in nuclear criticality accidents provided that the virgin fission neutrons are completely free from the scattered neutrons.

• Composites Research
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• v.24 no.1
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• pp.45-50
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• 2011

Transparent and conductive carbon nanotube on polyethylene terephthalate (PET) were prepared by dip-coating method for self-sensing multi-functional nanocomposites. The changes in the electrical and optical properties of CNT coating mainly depended on the number of dip-coating, concentration of CNT solution. Consequently, the surface resistance and transmittance of CNT coating were sensitively controlled by the processing parameters. Surface resistance of CNT coating was measured using four-point method, and surface resistance of coated CNT could be better calculated by using the dual configuration method. Optical transmittance of PET film with CNT coating was evaluated using UV spectrum. Surface properties of coated CNT investigated by wettability test via static and dynamic contact angle measurement were consistent with each other. As dip-coating number increased, surface resistance of coated CNT decreased seriously, whereas the transmittance exhibited little lower due to the thicker CNT networks layer. Interfacial microfailure properties were investigated for CNT and indium tin oxide (ITO) coatings on PET substrates by electrical resistance measurement under cyclic loading fatigue test. CNT with high aspect ratio exhibited no change in surface resistance up to 2000 cyclic loading, whereas ITO with brittle nature showed a linear increase of surface resistance up to 1000 cyclic loading and then exhibited the level-off due to reduced electrical contact points based on occurrence of many micro-cracks.

• Korean Journal of Optics and Photonics
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• v.28 no.6
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• pp.356-360
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• 2017

Indium tin oxide (ITO) provides high electrical conductivity and transparency at visible and near-IR wavelengths. ITO is widely used as a transparent electrode for the fabrication of LCDs, OLEDs, and many kinds of optical applications. It is widely employed for electrodes in various electric and display sectors because of its transparency in the visible range and high conductivity. Therefore, one issue is removing a specific area of a layer of material such as ITO or metallic film on a substrate, without affecting the properties of the substrate. ITO-on-glass removal using a laser is friendlier to the environment than traditional methods. In this study, ablation of ITO film on glass using a femtosecond-laser micromachining system (wavelength 1026 nm, pulse duration 150 fs) and a nanosecond-laser micromachining system (wavelength 1027 nm, pulse duration 5 ns) are described, compared, and analyzed.

• Applied Chemistry for Engineering
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• v.3 no.1
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• pp.88-99
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• 1992

For the development of semiconducting photoelectrode to be more stable and efficient in the process of photoelectrolysis of the water, pure titanium rods were oxidized by anodic oxidation, furance oxidation and flame oxidation and used as electrodes. The Indium islands were formed by electrodeposition of "In" thin film on $TiO_2$ and Ti by electrodeposition. Also $A1_2O_3$ and NiO islands were coated on Ti by the electron-beam evaporation technique. The maximum photoelectrochemical conversion efficiency(${\eta}$) was 0.98% for flame oxidized electrode($1200^{\circ}C$ for 2min in air). Anodically oxidized electrodes have photoelectrochemical conversion efficiency of 0.14%. Furnace oxidized electrode($800^{\circ}C$ for 10min in air) has 0.57% of photoelectrochemical efficiency and shows a band-gap energy of about 2.9eV. The $In_2O_3$ coated $TiO_2$ exhibits 0.8% of photoelectrochemical efficiency but much higher value of ${\eta}$ was obtained with the Increase of applied blas voltage. However, $Al_2O_3$ or NiO coated $TiO_2$ shows much low value of ${\eta}$. The efficiency was dependent on the presence of the metallic interstitial compound $TiO_{0+x}$(x<0.33) at the metal-semiconductor interface and the thickness of the suboxide layer and the external rutile scale.

• Journal of Sensor Science and Technology
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• v.1 no.1
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• pp.5-12
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• 1992

We have fabricated a-Si:H multilayer for contact-type linear image sensor by means of RF glow discharge decomposition method. The ITO/i-a-Si:H/Al structure has relatively high dark current due to indium diffusion and carrier injection from both electrodes, resulting in low photocurrent to dark current. To suppress the dark current and to enhance interface electric field between ITO and i-a-Si:H film we have fabricated ITO/insulator/i-a-S:H/p-a-S:H/Al multilayer film with blocking structure. The photocurrent of ITO/$SiO_{2}(300{\AA})$/i-a-Si:H/p-a-Si:H($1500{\AA}$)/Al multilayer sensor with 5V bias voltage became saturated at about 20nA under $20{\mu}W/cm^{2}$ light intensity, while the dark current was less than 0.1nA. To increase the light generation efficiency we have adopted ITO/$SiO_{x}N_{y}(300{\AA})$/i-a-Si:H/p-a-Si:H($1500{\AA}$)/Al structure, showing photocurrent of 30nA and dark current of 0.08nA with 5V bias voltage. Also the spectral photosensitivity of the multilayer was enhanced for short wavelength visible region of 560nm, compared with that of the a-Si:H monolayer of 630nm. And its photoresponse time was about 0.3msec with the film homogeneity of 5% deviation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.646-651
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• 2018

This paper reports that the electronic properties at a $P3HT/TiO_2$ interface associated with exciton dissociation and transport can be tailored by the insertion of a graphene quantum dot (GQD) layer. For donor/acceptor interface modification in an $ITO/TiO_2/P3HT/Al$ photovoltaic (PV) device, a continuous GQD film was prepared by a sonication treatment in solution that simplifies the conventional processes, including laser fragmentation and hydrothermal treatment, which limits a variety of component layers and involves low cost processing. The high conductivity and favorable energy alignment for exciton dissociation of the GQD layer increased the fill factor and short circuit current. The origin of the improved parameters is discussed in terms of the broad light absorption and enhanced interfacial carrier transport.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.600-613
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• 2018

The purpose of this research was to introduce a network analysis method for analyzing the recent trend of the flexible solar cell using a scholarly database. Based on the five years from 2013 to 2017, we used centrality analysis of research papers via measurement of degree centrality, closeness centrality, and betweenness centrality. The results of network analysis show that cell has a centrality value above 0.8, which means that cell is connected with 80% of the total keywords, so it is recognized as the center of flexible solar cell research. The analysis results also indicate that perovskite and copper indium gallium diselenide (CuInGaSe2, or CIGS) are the center of the subgroup for cell. We recognize that the result refers to recent new technology called the CIGS/perovskite tandem solar cell. We hope that the network analysis method will be the appropriate and precise tool for technology and research planning via elaboration and optimization.

• 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.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.463-463
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• 2014

Dye-sensitized solar cells (DSSCs) have generated a strong interest in the development of solid-state devices owing to their low cost and simple preparation procedures. Effort has been devoted to the study of electrolytes that allow light-to-electrical power conversion for DSSC applications. Several attempts have been made to substitute the liquid electrolyte in the original solar cells by using (2,2',7,7'-tetrakis (N,N-di-p-methoxyphenylamine)-9-9'-spirobi-fluorene (spiro-OMeTAD) that act as hole conductor [1]. Although efficiencies above 3% have been reached by several groups, here the major challenging is limited photoelectrode thickness ($2{\mu}m$), which is very low due to electron diffusion length (Ln) for spiro-OMeTAD ($4.4{\mu}m$) [2]. In principle, the $TiO_2$ layer can be thicker than had been thought previously. This has important implications for the design of high-efficiency solid-state DSSCs. In the present study, we have fabricated 3-D Transparent Conducting Oxide (TCO) by growing tin-doped indium oxide (ITO) nanowire (NWs) arrays via a vapor transport method [3] and mesoporous $TiO_2$ nanoparticle (NP)-based photoelectrodes were prepared using doctor blade method. Finally optimized light-harvesting solid-state DSSCs is made using 3-D TCO where electron life time is controlled the recombination rate through fast charge collection and also ITO NWs length can be controlled in the range of over $2{\mu}m$ and has been characterized using field emission scanning electron microscopy (FE-SEM). Structural analyses by high-resolution transmission electron microscopy (HRTEM) and X-Ray diffraction (XRD) results reveal that the ITO NWs formed single crystal oriented [100] direction. Also to compare the charge collection properties of conventional NPs based solid-state DSSCs with ITO NWs based solid-state DSSCs, we have studied intensity modulated photovoltage spectroscopy (IMVS), intensity modulated photocurrent spectroscopy (IMPS) and transient open circuit voltages. As a result, above $4{\mu}m$ thick ITO NWs based photoelectrodes with Z907 dye shown the best performing device, exhibiting a short-circuit current density of 7.21 mA cm-2 under simulated solar emission of 100 mW cm-2 associated with an overall power conversion efficiency of 2.80 %. Finally, we achieved the efficiency of 7.5% by applying a CH3NH3PbI3 perovskite sensitizer.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.383-383
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• 2014

최근 디스플레이, 태양전지 그리고 touch screen panels 등 optoelectronic 장치의 시장이 성장함에 따라 투명전극의 수요가 증가하고 있다. Indium tin oxide (ITO)의 좋은 특성 때문에 주로 투명전극에 많이 사용되고 있다. 그러나 화학적 안정성이 떨어지고, 휘어질 때 특성저하가 심하여 금속나노와이어, 탄소나노튜브, 전도성폴리머, 그리고 그래핀 등의 다른 투명전극의 연구가 활발히 진행되고 있다. 그 중에서 그래핀은 높은 전자 이동도(200000 cm2v-1s-1)와 휘어져도 전기적 크게 변하지 않는 특성 때문에 유망한 투명 전도성 전극 (Transparent Conductive Electrodes, TCEs)으로 연구되어왔다. 또한 다양한 속성 가운데, 높은 광 투과성은 그래핀의 가장 큰 장점이다 [1]. 최근, 화학 기상 증착 (Chemical Vapor Deposition, CVD) 등 다양한 제조 방법이 대량 생산을 위해 개발되었다. 그러나 이 방법은 비용이 많이 들며, 과정이 상당히 복잡하고 높은 온도 (${\sim}1000^{\circ}C$)를 필요로 한다. 따라서 용매 기반의 환원된 그래핀 산화물(Reduced Graphene Oxides, RGOs)이 최근 주목 받고 있다. 그러나 RGOs의 면저항이 높아 전극으로서 사용이 제한된다. 따라서 전기적 특성을 향상시키는 방법으로 단일 벽 탄소 나노튜브 (Single-Walled Carbon Nanotubes, SWNTs)를 혼합하거나 화학적 도핑을 통하여 면저항을 크게 향상시키는 연구가 활발히 진행되고 있다. 그러나 이런 화학적 도핑의 경우 박막이 공기 중에 직접 산소나 습기와 반응하여 전기적 특성이 저하되는 문제점을 가지고 있다 [2]. 이러한 문제를 해결하기 위해 AuCl3을 도핑한 박막에 내열성 및 내광성 등의 화학적 안정성이 뛰어난 PEDOT:PSS를 코팅하여 필름의 공기중의 노출을 막아 줌으로써 도핑의 안전성 및 전기적 특성을 최적화하였다. 본 연구에서는 간단한 dip-coating방법을 사용하여 4개의 RGO/SWNTs 박막을 흡착하였다. 다음으로 AuCl3를 도핑하여 면저항 $4.909K{\Omega}$, $4.381K{\Omega}$인 두 개의 샘플의 시간과 온도에 따른 면저항의 변화를 확인하였다. 그리고 필름의 도핑 안전성을 향상 시키기 위해 AuCl3를 도핑한 필름 위에 전도성 폴리머 PEDOT:PSS 코팅하여 면저항 $886.1{\Omega}$, $837.5{\Omega}$인 두 개의 샘플의 시간과 온도에 따른 면저항의 변화를 확인하였다. AuCl3 도핑된 필름의 경우 공기 중에 150시간 노출 시 72%의 면저항 증가가 발생하였지만 PEDOT:PSS가 코팅된 필름의 경우 5%의 면저항 증가가 나타나 확연한 차이를 보였다. 또한 AuCl3 도핑한 필름의 경우 $150^{\circ}C$에서 60시간동안 공기중에 노출되었을 때 525%의 면저항 증가가 발생하였지만 PEDOT:PSS가 코팅된 필름의 경우 58%의 면저항 증가를 나타내었다. 이것은 PEDOT:PSS가 passivation역할을 하여 필름이 공기에 노출된 부분을 막아주어 도핑된 필름의 면저항의 변화를 줄여 주었음을 알 수 있다.