• Journal of Sensor Science and Technology
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• v.5 no.5
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• pp.39-46
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• 1996

The Pd or Pt-doped $WO_{3}$ thin-film NOx sensor was fabricated. The $WO_{3}$-based thin films as a gas-sensing layer were deposited at ambient temperature in a high-vacuum resistance heated evaporator and annealed at $500^{\circ}C$. The gas sensitivity ($R_{gas}/R_{air}$) to 5 ppm $NO_{2}$ measured at the operating temperature of $300^{\circ}C$ was 50 (highest sensitivity) for the 0.5 wt.% $Pt-WO_{3}$ sensor.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.4
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• pp.29-34
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• 2008

Generally, for conventional 3-D Hall sensor it is general that the sensitivity for $B_z$ is about 1/10 compared with those for $B_x$ or $B_y$. Therefore, in this work, we proposed 3-D Hall sensor with new structures. We have increased the sensitivity about 6 times to form the trench using anisotropic etching. And we have increased the sensitivity for the $B_z$ by 80 % compared with those of $B_x$ and $B_y$ using deposition of the ferromagnetic thin films on the bottom surface of the wafer to concentrate the magnetic fluxes. Sensitivities of the fabricated sensor with Ni/Fe film for $B_x,\;B_y$, and $B_z$ were measured as 361mV/T, 335mV/T, and 286mV/T, respectively. It has also showed sine wave of Hall voltages over a $360^{\circ}$ rotation. A packaged sensing part was $1.2{\times}1.2mm^2$. The measured linearity of the sensor was within ${\pm}3%$ of error. Resolution of the fabricated sensor was measured by $1{\times}10^{-5}T$.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.7
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• pp.26-33
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• 1999

In order to examine the effect of beam location n the performance of bridge type piozoresistive silicon accelerometer, three sensors having different location of beams were simulated by FEN(finite element method) and fabricated by RIE(reactive ion etching) and KOH etching method using SDB(silicon direct bonding) wafer, Results of the FEM simulation present that the 1st resonace frequency and Z axis sensitivity of each sensor are identical but the 2nd, and the 3rd resonace frequency and X, Y axis sensitivity are different. Even though the 1st resonance frequency and Z axis sensitivity measured from fabricated sensors do not perfectly coincide with each other, all 3 type sensors present 180 ~ 220N/G of Z sensitivity at 5 V supply voltage and 1.3 ~ 1.7kHz of the 1st resonance frequency and about 2% of lateral sensitivity.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.11
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• pp.9-17
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• 2000

A sensor array with 10 discrete sensors integrated on a substrate was developed for discriminating the kinds and quantities of explosive gases. The sensor array consisted of 10 oxide semiconductor gas sensors with $SnO_2$ as base material and had broad sensitivity to specific gas. The sensor array was designed with uniform thermal distribution and had also high sensitivity and reproductivity to low gas concentration through nano-sized sensing materials with different additives. By using the sensitivity signal of the sensor array at $400^{\circ}C$, we could reliably discriminate the kinds and quantities of explosive gases like butane, propane and methane under the lower explosion limit through the principal component analysis (PCA) method.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.1
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• pp.11-19
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• 2003

A micro sensor array with 4 discrete sensors integrated on a microhotplate was developed for identifying the kinds and quantities of explosive gases. The sensor array consisited of four tin oxide-based thin films with the high and broad sensitivity to the tested explosive gases and uniform thermal distribution on the plate. The microhotplate, using silicon substrate with N/O/N membrane, dangling in air by Al bonding wires, and controlling the thickness by chemical mechanical process (CMP), has been designed and fabricated. By employing the sensitivity signal of the sensor array at 40$0^{\circ}C$, we could reliably classily the kinds and quantities of the explosive gases like butan, propane, LPG, and carbon monoxide within the range of threshold limit values (TLVs), employing principal component analysis (PCA).

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.1
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• pp.26-33
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• 2011

In this study, a high-sensitive smart wireless sensor based on an Imote2 sensor platform is developed for structural health monitoring of harbor structures. To achieve the objective, the following approaches are implemented. Firstly, the smart wireless sensor based on the high-performance Imote2 sensor platform is designed to measure acceleration with high sensitivity from structures. Secondly, embedded software is designed for autonomous structural health monitoring. Finally, the performance of the smart wireless sensor is estimated from experimental tests on a lab-scaled caisson structure.

• The Journal of the Acoustical Society of Korea
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• v.19 no.2
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• pp.8-12
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• 2000

This paper describes the sensitivity stability of a mandrel type fiber optic acoustic sensor with respect to its environmental conditions such as hydrostatic pressure and underwater temperature. The sensors under consideration have various mandrel structures such as a cylindrical mandrel, a concentric composite mandrel, and an air-backed concentric composite mandrel. The analysis results show that the sensors have such good robustness, less than 0.15dB, in its sensitivity with respect to the variation in hydrostatic pressure. Further, the nylon concentric composite mandrel type sensor including an air cavity turns out to have the most superior stability than others to the underwater temperature variations.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.337-337
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• 2008

Acoustic emission(AE) 센서의 감도개선을 위해 적합한 압전소자의 특성향상에 대해 연구하였다. AE 센서기술은 재료 내부에 마이크로크랙에 의해 변형과 손상이 생길 때 발생하는 기계적인 진동을 고감도 압전소자를 통해 전기적인 신호로 변환해 재료의 이상 유무를 알 수 있는 유용한 방법이다. AE 센서는 압전소자와 구리 캡 그리고 구리와 황동재질의 떨림판으로 구성되어 있다. 재료의 손상을 알기위한 변위가 낮을 경우 약한 AE 신호가 발생하며 검출하기가 어렵다. 미세변위에 의한 AE신호를 검출하기 위해서는 우수한 전기기계결합계수 (kp)와 압전상수($d_{33}$)를 갖는 압전소자가 필요하다. 이에 본 연구에서는 Pb$(Zr_{0.54}Ti_{0.46})O_3$ + x wt%$Cr_2O_3$ + y wt%$Nb_2O_5$ 조성에서 $Cr_2O_3$, $Nb_2O_5$ 첨가량 x, y 변화에 따른 압전특성과 AE센서특성을 고찰하였다.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.1
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• pp.19-24
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• 1999

$In_2O_3$-based thick films for the ozone detection of ppb range have been investigated. The $In_2O_3$ sensing layer is quite sensitive to ozone, but the saturated stable sensitivity cannot be obtained at the ozone exposure of 100 ppb for 5 min. The addition of $Fe_2O_3$ into $In_2O_3$ indicates some improvement in response time and sensitivity, but it seems the improvement is not good enough for real applications. Firing of $In_2O_3$:$Fe_2O_3$ powder induces remarkable improvement in response and recovery, although the sensitivity decrease. The sensing layer fired at $1300^{\circ}C$ and operated $550^{\circ}C$ shows excellent properties of fast response time, saturated stable sensitivity and rapid recovery characteristics to 100 ppb ozone exposure for 5 min. Especially, it shows the reproducibility of the sensor signal for repeated measurements and the linearity between the ozone concentration and the sensor resistance. The preliminary results clearly demonstrated that the sensor can be successfully applied for the ozone detection of ppb range.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.386.2-386.2
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• 2014

본 연구에서는 바이오 센서 응용을 위해 그래핀을 전극으로 제작하여 그래핀 표면 결함준위에 따른 센서의 민감도를 전기화학 실험을 통해 관찰하였다. 그래핀은 니켈/구리촉매를 이용한 저 진공 화학 기상 증착 장비(Low-Pressure Chemical Vapor Deposition; LP-CVD)와 Photo-lithography로 제작한 것과 탄소 산화물을 환원시켜 만든 환원-그래핀, 두 가지를 사용하였다. 전기화학 실험에서 그래핀 전극 및 Silver/Silver chloride (Ag/AgCl), Fluorine doped Tin Oxide (FTO)은 작업 전극 및 기준 전극, 상대 전극으로 각각 사용하였고, 반응용액은 potassium hexacyanoferrate (III)를 농도를 다르게 하여 사용하였다. 그래핀의 표면 상태, 층수, 결함 정도 등 구조적인 특성은 원자력현미경(Atomic Force Microscopy; AFM), 주사 전자 현미경(Secondary Electron Microscopy; SEM)과 Raman spectroscopy를 각각 이용하여 확인하였고, 그래핀의 결함준위에 따른 반응면적 및 센서 감도 의존성을 전류모드-원자력현미경(Current-Atomic Force Microscopy; I-AFM)과 전기화학 임피던스 분광법(Electrochemical Impedance Spectroscopy; EIS)를 통해 그래핀 전극의 성능을 분석하고, 그래핀 결함 준위에 따른 센서 감도 의존성은 순환전위 분광법 (Cyclic Voltammetry; CV)를 이용하여 관찰하였다. 또한 농도가 다른 반응용액은 센서의 민감도를 관찰하는데 사용하였다. 결과적으로 LP-CVD로 성장한 그래핀과 환원-그래핀의 결함준위에 따른 센서의 성능을 비교 분석한 결과와 반응용액 농도에 따른 센서의 민감도 결과는 그래핀 바이오센서에 대한 응용 및 상용화를 앞당기는데 기여할 것으로 예상한다.