• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.460-463
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• 2004

본 논문은 고에너지 방사선 검출을 위한 흔합형 구조의 방사선 센서를 제작, 반응 특성을 평가하였다. 먼저, 스크린 인쇄법을 이용하여 형광체 필름을 제작하였으며, 발광스펙트럼(PL, Photoluminescence) 및 잔광 시간(decay time) 측정을 통하여 형광체의 발광 특성을 조사하였다. 제작된 혼합구조의 방사선 센서는 $2{\mu}m$ 두께의 $HgI_2$와 $150{\mu}m$ 두께의 형광체 필름으로 제작되었으며, 면적은 $2\;cm\;{\times}\;2\;cm$이다. 방사선에 대한 전기적 검출 신호의 특성을 조사하기 위해 인가전압에 따른 암전류 및 방사선민감도, 선량에 따른 검출신호를 측정하였다. 측정결과, 제작된 $HgI_2$ 필름은 방사선에 의해 형광체에서 방출된 가시광 파장을 잘 흡수하였으며, 진단영역의 저에너지 방사선에 의해 직접 전기적 신호를 발생시켜 높은 방사선 민감도를 보였다. 뿐만 아니라, 인가전압에 대해 $10\;pA/mm^2$이하의 낮은 암전류를 가졌으며, 넓은 조사선량에서 우수한 선형성을 보였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.152-153
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• 2012

Ion sensitive field effect transistor (ISFET)는 전해질 속 각종 이온농도를 측정하는 반도체 이온 센서이다. 이 소자의 기본 구조는 metal oxide semiconductor field effect transistor (MOSFET)에서 고안되었으며 게이트 컨택 부분이 기준전극과 전해질로 대체되어진 구조를 가지고 있다 [1]. ISFET는 기존의 반도체 CMOS 공정과 호환이 가능하고 제작이 용이할 뿐만 아니라, pH용액에 대한 빠른 반응 속도, 비표지 방식의 생체물질 감지능력, 낮은 단가 및 소자의 집적이 용이하다는 장점을 가지고 있다. ISFET pH센서의 감지특성에 결정하는 요소 중 가장 중요한 것은 소자의 감지막이라고 할 수 있다. 감지막은 감지 대상 물질과 물리적으로 직접 접촉되는 부분으로서 일반적으로 기계적/화학적 강도가 우수한 실리콘 산화막(SiO2)이 많이 사용되어져 왔다. 최근에는 기존의 SiO2 보다 성능이 향상된 감지막을 개발하기 위하여 Al2O3, HfO2, ZrO2, 그리고 Ta2O5와 같은 고유전 상수(high-k)를 가지는 물질들을 EIS 센서의 감지막으로 이용하는 연구가 활발하게 진행되고 있다. 하지만 지속적인 high-k 물질들에 대한 연구에도 불구하고 각각의 물질이 갖는 한계점이 드러났다. 본 연구에서는 SOI기판에서 SiO2 /HfO2 (OH), SiO2/Al2O3 (OA) 이단 적층 그리고 SiO2/HfO2/Al2O3 (OHA) 삼단적층 감지막을 갖는 ISFET을 제작하고 각 감지막의 특성을 평가하였다. 평가된 특성의 결과가 아래의 표1에 요약되었다. 그 결과, 각 high-k 물질이 갖는 한계점을 극복하기 위하여 제안된 OHA감지막은 기존에 OH, OA가 갖는 장점을 취하면서 단점을 최소화 시키는 최적화된 감지막의 감지특성을 보였다.

• Journal of Sensor Science and Technology
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• v.5 no.1
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• pp.15-22
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• 1996

FET type $Ca^{2+}$ sensor(Ca-ISFET) was fabricated by micropool and photolithographic method utilizing photosensitive polymer as membrane materials. When OMR-83 negative photoresist was used as membrane material, it gave good sensitivity by micropool method with dioctyladipate as plasticizer but it could not be used in the photolithographic method. When poly(viny1 butyral), PVB was used as membrane material, it gave relatively high sensitivity ($23{\pm}0.2\;mV/decade$) for $Ca^{2+}$ concentration range of $10^{-4}{\sim}10^{-1}\;mole/{\ell}$ by photolithographic method. PVB also provided good adhesion to the pH-ISFET base device without adhesion promoter pretreatment and any plasticizer.

• Journal of the Korean Chemical Society
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• v.46 no.5
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• pp.407-411
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• 2002

A method to determine lead ion in aqueous media using an optical sensor loaded on a fluorescent optode membrane incoporating a metal ion-selective ionophore, a proton-selective chromoionophore and lipophilic anionic sites has been studied. The effects of pH and thickness of membrane on the fluorescence intensity were investigated. The effects of foreign ions such as $Na^+$, $K^+$, $Mn^{2+}$ and $Zn^{2+}$ on the determination of lead ion were also studied. The linear range in the calibration curve for the determination of lead ion was found to be 5.0${\times}10^-7$ to 5.0${\times}$$10^-3$M and the correlation coefficient in this range was -0.99107 under the optimal experimental conditions. The relative standard deviation of the blank signals was 3.0% and the detection limit of lead ion was 5.0${\times}$$10^-9$M.

• Korean Journal of Optics and Photonics
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• v.25 no.2
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• pp.95-101
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• 2014

When voltage is applied on the metal layer of a surface plasmon resonance (SPR) sensor, electric field excitation causes charge accumulation on the metal surface. This alters not only the optical properties of the metal but also the SPR angle. In this study we investigate this effectby performing experiments using solutions of various pH values, and we obtain the relation between total surface charge and SPR angle. The curves for the various pH conditions become coincident. We compare our results to those from an earlier space charge layer (SCL) model, and suggest a modified SCL model which explains our result well. This result will be useful in applications of SPR sensors, and in studying the optical properties of thin metal layers.

• Journal of IKEEE
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• v.26 no.2
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• pp.219-225
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• 2022

The textile industry in Korea, the dyeing sector is an energy-intensive sector and has low per-unit productivity due to its labor-intensive nature. If the defective rate of dyed fabrics is high, additional costs are incurred due to an increase in production cost due to re-dyeing. Therefore, the goal of the dyeing factory was to minimize the defect rate rather than to save energy. It was difficult to check the dyeing state of the fabric in real time due to the risk of accidents due to burns or pressure when dyeing in a high-temperature and high-pressure environment. In this paper, a complex sensor that can measure the exhaustion rate of dye solution in the dyeing machine using turbidity, pH, and conductivity sensors was proposed, and the experimental method and experimental results were analyzed.

• Journal of Sensor Science and Technology
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• v.6 no.4
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• pp.258-264
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• 1997

$YBa_{2}Cu_{3}O_{7}$ single layer dc SQUID magnetometers, prepared on $1\;cm^{2}\;SrTiO_{3}$ substrates, have been fabricated and characterized. Based on the analytical description, a SQUID magnetometer design having a 8.5 mm pickup coil with 2.6 mm linewidth, and a SQUID inductance Ls = 50 pH with $3\;{\mu}m$ Josephson junctions is presented. The devices showed a maximum modulation voltage depth of $65\;{\mu}V$ and a magnetic field noise of 0.6 pT /$\sqrt{Hz}$ at 1 Hz. Clear traces of human magnetocardiogram could be obtained with the SQUID magnetometer operating at 77 K.

• Journal of the Korean Electrochemical Society
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• v.17 no.3
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• pp.164-171
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• 2014

A highly sensitive and selective non-enzymatic glucose sensor has gained great attention because of simple signal transformation, low-cost, easily handling, and confirming the blood glucose as the representative technology. Until now, glucose sensor has been developed by the immobilization of glucose oxidase (GOx) on the surface of electrodes. However although GOx is quite stable compared with other enzymes, the enzyme-based biosensors are still impacted by various environment factors such as temperature, pH value, humidity, and toxic chemicals. Non-enzymatic sensor for direct detecting glucose is an attractive alternative device to overcome the above drawbacks of enzymatic sensor. Many efforts have been tried for the development of non-enzymatic sensors using various transition metals (Pt, Au, Cu, Ni, etc.), metal alloys (Pt-Pb, Pt-Au, Ni-Pd, etc.), metal oxides, carbon nanotubes and graphene. In this paper, we show that Ni-based nano-particles (NiNPs) exhibit remarkably catalyzing capability for glucose originating from the redox couple of $Ni(OH)_2/NiOOH$ on the surface of ITO electrode in alkaline medium. But, these non-enzymatic sensors are nonselective toward oxidizable species such as ascorbic acid the physiological fluid. So, the anionic polymer was coated on NiNPs electrode preventing the interferences. The oxidation of glucose was highly catalyzed by NiNPs. The catalytically anodic currents were linearly increased in proportion to the glucose concentration over the 0~6.15 mM range at 650 mV versus Ag/AgCl.

• Analytical Science and Technology
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• v.20 no.5
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• pp.393-399
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• 2007

In principle, the blood galactose level may be determined conveniently with a strip-type biosensor similar to that for glucose. In this study, we describe the development of a disposable galactose biosensor strip for point-of-care testing. The sensor strip is constructed with screen-printed carbon paste electrode (SPCE) and sample amount (< $100{\mu}L$). The developed strip the galactose level in less than 90 s using bienzymatic system of galactose oxidase (GAO) and horseradish peroxidase (HRP). The effects of pH, mediator (1,1-ferrocenedimethanol) concentration, ratio of enzymes, and applied potential were determined preliminarily with glassy carbon electrodes, and optimized further with the strip-type electrodes. The sensor exhibits linear response in the range of $0{\sim}400{\mu}M$ ($r^2$ = 0.997, S/N = 3). Since a low working potential, in principle, the fabricated disposable galactose biosensor has -100 mV (vs. Ag/AgCl), it is applied for the detection of galactose, interfering responses from common interferents such as ascorbic acid, uric acid and acetaminophen could be minimized. The sensor has been used to determine the total galactose level in standard samples with satisfactory reproducibility (CV = 5 %).

• Journal of Sensor Science and Technology
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• v.16 no.3
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• pp.234-239
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• 2007

Crystallographically {h00}-oriented $0.94(Bi_{0.5}Na_{0.5})TiO_{3}-0.06BaTiO_{3}$ (0.94BNT-0.06BT) ceramics was prepared by the Reactive Templated Grain Growth (RTGG) method using the $Bi_{4}Ti_{3}O_{12}$ template. The sheets prepared by tape-casting of slurries containing the templates and starting materials are cut, laminated, and pressed. Then burn-out and sintering was conducted. Also, to compare with the 0.94BNT-0.06BT ceramics prepared by the RTGG method another 0.94BNT-0.06BT ceramics was prepared by the solid-state method. In the optimum of this experiments range, the degree of orientation of the 0.94BNT-0.06BT ceramics prepared by the RTGG method was texture fraction${\approx}92%$ and the piezoelectric constant($d_{33}$) and coupling factor($k_{p}$) was obtained to $d_{33}{\approx}205{\;}pC/N$, $k_{p}{\approx}0.33%$, respectively.