• 센서학회지
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• 제17권5호
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• pp.361-368
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• 2008

Nanosized $SnO_2$ particles were synthesized by homogeneous precipitation method using tin chloride ($SnCl_4{\cdot}5H_{2}O$) and urea ($CO(NH_2)_2$). The powders were heated at $500^{\circ}C$ and $600^{\circ}C$ for 2h. The crystal structure, microstructure, thermal behavior, specific surface area were analyzed using XRD, FE-SEM, TGA and BET, respectively. The initial resistance and the $H_2$ sensing properties were measured as a function of ${Sb_2}{O_3}$ and Pd doping concentrations. The resistance was decreased with the addition of ${Sb_2}{O_3}$ and the sensitivity for $H_2$ gas was increased with the addition of Pd. Thus, the optimum $H_2$ gas sensing property was obtained in the 0.25.mol% ${Sb_2}{O_3}$ and 1.w% added $SnO_2$ powders.

• 센서학회지
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• 제17권1호
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• pp.9-14
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• 2008

In this paper, the gas responses of tungsten oxide films prepared by anodic reaction was discussed. Sensing electrodes and heating electrodes were patterned by photolithography method on quartz substrate. Porous tungsten oxide was fabricated in electrolyte solutions of 5 % HF (HF :$C_2H_6OH:H_2O$=3 : 2 : 20) by anodic reaction. The anodic reaction with metal (platinum wire) as a cathode and the sensing device as an anode was conducted under the various reaction times (1-10 min) at 10 mA/$cm^2$ The surface structure and morphology of the fabricated sensor have been analysed by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). All the peaks of XRD results were well indexed to the pure phase pattern. The average diameter of the porous tungsten oxide surface were ranged about 100 nm. The fabricaed sensor showed good sensitivity to 200 ppm toluene at operating temperature of $250^{\circ}C$.

• 한국자기학회지
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• 제16권3호
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• pp.157-162
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• 2006

이온빔 증착 스퍼터링법과 고아 리소그래피법으로 FeMn-스핀밸브 바이오 센서를 제작하였다. 혈액내의 Fe를 포함한 헤모글로빈(Hemoglobin)과 나노 자성입자의 자성검출은 최대 자장감응 약 $0.1{\sim}0.8%/Oe$인 거대자기저항 스핀밸브 바이오 센싱소자를 이용하였다. 사용된 혈액은 인체의 피였고, Co-페라이트 나노 자성입자는 수용성 무정형 실리카로 코팅이 되었으며, 그 크기의 평균직경의 범위는 9nm에서 50nm이었다. 실제 크기가 $5x10{\mu}m^2 $ 혹은 $2x6{\mu}m^2 $로 제작된 센싱소자의 4 전극 중 전류 입력단자에 흐르는 감지전류는 1 mA로 하였다. 혈액과 나노자성 입자가 소자의 중앙부분으로 떨어졌을 때, 출력신호는 각각 자성 여부의 검출 특성을 알 수 있는 충분한 크기로 나타났다.

• 한국자기학회지
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• 제10권4호
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• pp.159-163
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• 2000

절연층으로 CoO를 사용한 스핀의존성 터널링 접합 NiFe(30 nm)/CoO(t)/Co(30 nm-t)에서 터널링 자기저항성질을 연구하였다. 3-gun 스퍼터링 시스템에서 4$^{\circ}$tilt-cut (111)Si을 기판으로, 상부자성층으로 Ni$_{80}$Fe$_{20}$를 사용하였고 Co를 하부 자성층으로 사용하였다. 절연층으로 사용된 CoO른 하부 자성층 Co를 산소 플라즈마 산화법과 상온에서의 자연산화를 통해 얻었다. CoO를 플라즈마 산화법으로 얻은 경우 플라즈마 산화시간이 증가할수록 자기이력곡선에서 반강자성 물질인 CoO에 의해 NiFe와 Co의 보자력이 증가하는 것을 관찰할 수 있었다. 플라즈마 산화된 CoO의 경우, 상온에서 1mA의 감지전류를 흘려줬을 경우 최대 1.2 %의 자기저항비를 얻을 수 있었다. 자연산화법으로 CoO를 얻은 경우 감지 전류 1 mA에서 4.8 %의 자기저항비를 관찰할수 있었고, 감지전류 1.5 mA의 경우 28 %의 자기저항비와 10.9 ㏀$\times$$\mu\textrm{m}$$^2$의 값을 얻을 수 있었다. 저항$\times$면적값이 2.28 ㏀$\times$$\mu\textrm{m}$$^2$일 때 최대 120 %의 자기저항비를 얻을 수 있었다.다.

• 한국표면공학회지
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• 제50권4호
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• pp.296-300
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• 2017

NiO nanofibers with Au nanoparticles were synthesized by sol-gel and electrospinning techniques, in which the reduction process by ultraviolet exposure is included for the growth of Au nanoparticles in the electrospinning solution. FE-SEM(Field Emission Scanning Electron Microscopy), TEM(Transmission Electron Microscopy) revealed that the synthesized nanofibers had the diameter of approximately 200 nm. X-ray diffraction showed the successful formation of Au-decorated NiO nanofibers. Gas sensing tests of Au-decorated NiO nanofibers were performed using reducing gases of CO, and $C_6H_6$, $C_7H_8$, $C_2H_5OH$. Compared to as-synthesized NiO nanofibers, the response of Au-loaded NiO nanofibers to CO gas was found to be about 3.4 times increased. On the other hand, the response increases were only 1.1-1.3 times for $C_6H_6$, $C_7H_8$, and $C_2H_5OH$.

• Journal of information and communication convergence engineering
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• 제2권1호
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• pp.22-25
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• 2004

A highly sensitive ammonia gas sensor using thick-film technology has been fabricated and examined. The sensing material of the gas sensor is FeOx-$WO_{3}-SnO_{2}$ oxide semiconductor. The sensor exhibits resistance increase upon exposure to low concentration of ammonia gas. The resistance of the sensor is decreased, on the other hand, for exposure to reducing gases such as ethyl alcohol, methane, propane and carbon monoxide. A novel method for detecting ammonia gas quite selectively utilizing a sensor array consisting of an ammonia gas sensor and a compensation element has been proposed and developed. The compensation element is a Pt-doped $WO_{3}-SnO_{2}$gas sensor which shows opposite direction of resistance change in comparison with the ammonia gas sensor upon exposure to ammonia gas. Excellent selectivity has been achieved using the sensor array having two sensing elements.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.172-176
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• 2002

This paper describes a MEMS-based micro-fluxgate magnetic sensing element using Ni$\_$0.8/Fe$\_$0.2/ film formed by electroplating. The micro-fluxgate magnetic sensor composed of a thin film magnetic core and micro-structured solenoids for the pick-up and the excitation coils, is developed by using MEMS technologies in order to take advantage of low-cost, small size and lower power consumption in the fabrication. A copper with 20um width and 3um thickness is electroplated on Cr(300${\AA}$)/Au(1500${\AA}$) films for the pick-up(42turn) and the excitation(24turn) coils. In order to improve the sensitivity of the sensing element, we designed the magnetic core into a rectangular-ring shape to reduce the magnetic flux leakage. An electroplated permalloy film with the thickness of 3 $\mu\textrm{m}$ is obtained under 2000Gauss to induce magnetic anisotropy. The magnetic core has the high DC effective permeability of ∼1,100 and coercive field of -0.1Oe. The fabricated sensing element using rectangular-ring shaped magnetic film has the sensitivity of about 150V/T at the excitation frequency of 2MHz and the excitation voltage of 4.4Vp-p. The power consumption is estimated to be 50mW.

• 한국전기전자재료학회논문지
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• 제16권2호
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• pp.120-124
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• 2003

This paper describes a MEMS-based micro-fluxgate magnetic sensing element using Ni$\_$0.8/Fe$\_$0.2/ film formed by electroplating. The micro-fluxgate magnetic sensor composed of a thin film magnetic core and micro-structure solenoids for the pick-up and the excitation coils, is developed by using MEMS technologies in order to take advantage of low-cost, small size and lower power consumption in the fabrication. A copper with 20${\mu}$m width and 3${\mu}$m thickness is electroplated on Cr (300${\AA}$) / Au (1500${\AA}$) films for the pick-up (42turn) and the excitation (24turn) coils. In order to improve the sensitivity of the sensing element, we designed the magnetic core into a rectangular-ring shape to reduce the magnetic flux leakage. An electroplated permalloy film with the thickness of 3${\mu}$m is obtained under 2000 gauss to induce magnetic anisotropy. The magnetic core has the high DC effective permeability of ~1,100 and coercive field of ~0.1 Oe. The fabricated sensing element using rectangular-ring shaped magnetic film has the sensitivity of about 150 V/T at the excitation frequency of 2 MHz and the excitation voltage of 4.4 V$\_$p p/. The power consumption is estimated to be 50mW.

• 한국자기학회지
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• 제17권4호
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• pp.156-161
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• 2007

어레이(away) 자성센서 개발을 위해 고진공 스퍼터링 증착장비를 이용하여 스펙큘러형(specular type) Glass/Ta(5)/NiFe(7)/IrMn(10)/NiFe(5)/$O_2$/CoFe(5)/Cu(2.6)/CoFe(5)/$O_2$/NiFe(7)/Ta(5)(nm) 거대자기저항-스핀밸브(giant magnetoresistive-spin valves; CMR-SV)박막을 제작하였다. 다층박막 시료를 $20{\times}80{\mu}m^2$의 미세 활성영역을 가진 15개 어레이를 $8{\times}8mm^2$ 영역 내에 최적화한 제작 조건으로 광 리소그래피 패터닝 하였다. Cu를 증착하여 만든 2단자 전극법으로 측정한 자성특성은 15개 모든 소자들이 균일한 자기저항특성을 나타내었고, 5 Oe 근방에서 가장 민감한 자기저항비 자장민감도와 출력전압들은 각각 0.5%/Oe, ${\triangle}$V: 3.9 mV이었다. 형상자기이방성이 적용된 상부 자유층 $CoFe/O_2/NiFe$층은 하부 고정 자성층 $IrMn/NiFe/O_2/CoFe$층 자화 용이축과 직교하였다. 측정시 인가전류 값을 각각 1 mA에서 10 mA까지 인가하였을 때 출력 작동 전압 값은 균일하게 증가하였으며, 자장감응도도 거의 일정하여 미세 외부자장에 민감한 나노자성소자로서 좋은 특성을 띠었다.

• 한국자기학회지
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• 제20권2호
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• pp.35-40
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• 2010

NiFe/Cu/NiFe/IrMn 스핀밸브 박막소자에 대해 자화 용이축에 의존하는 형상 자기이방성을 조사하였다. Ta(5 nm)/NiFe(8 nm)/Cu(2.3 nm)/NiFe(4 nm)/IrMn(8 nm)/Ta(2.5 nm) 다층박막을 증착할 때 350 Oe의 자기장으로 인가한 자화 용이축을 폭 방향 또는 길이 방향으로 설정하여 $1\;{\mu}m\;{\times}\;18\;{\mu}m$의 소자를 제작하였다. 2단자 방법으로 소자의 자기저항 곡선으로부터 자장감응도를 측정하고 자화 용이축에 따른 형상 자기이방성을 비교하였다. 측정한 소자 길이 방향의 센싱전류와 고정층의 자화 용이축이 소자 폭방향 각도가 GMR-SV 소자를 바이오센서로 활용하는데 중요한 요인임을 확인하였다.