• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.5
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• pp.288-293
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• 2017

$Fe_2O_3$ is one of the most important metal oxides for gas sensing applications because of its low cost and high stability. It is well-known that the shape, size, and phase of $Fe_2O_3$ have a significant influence on its sensing properties. Many reports are available in the literature on the use of $Fe_2O_3$-based sensors for detecting gases, such as $NO_2$, $NH_3$, $H_2S$, $H_2$, and CO. In this paper, we investigated the gas-sensing performance of a Pt-doped ${\varepsilon}$-phase $Fe_2O_3$ gas sensor. Pt-doped $Fe_2O_3$ nanoparticles were synthesized by a Sol-Gel method. Platinum, known as a catalytic material, was used for improving gas-sensing performance in this research. The gas-response measurement at $300^{\circ}C$ showed that $Fe_2O_3$ gas sensors doped with 3%Pt are selective for $NO_2$ gas and exhibita maximum response of 21.23%. The gas-sensing properties proved that $Fe_2O_3$ could be used as a gas sensor for nitrogen dioxide.

• Journal of the Korean Ceramic Society
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• v.27 no.4
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• pp.529-535
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• 1990

This paper describes the factors which control the impedance-relative humidity characteristics of the TiO2-V2O5 humidity sensor. To obtain the quantitative relationships between impedance and many manufacturing parameters such as V2O5mol%, the sintering time and temperature, various sets of samples are preared and tested. With changing relative hymidity from 20% to 80%, it is measrued that the corresponding capacitance and impedance from the semicircles which complex impedance plots make. As a result we found that the impedance-relative humidity characteristics are mainly controlled by the doping amount of V2O5 total pore volume and bulk resistence of the elements. We can assume the equivalent circuits of each samples and finally control the sintering time to get a linear humidity impedance response curve which plays an important role in device making. 4mol% V2O5-TiO2 specimen sintered at 90$0^{\circ}C$ for 10min. show liear log(Z) vs. RH characteristics and 10mol% V2O5-TiO2 specimen sintered at the same temp. for 20min. show linear (Z) vs. RH.

• Journal of Sensor Science and Technology
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• v.4 no.3
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• pp.15-21
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• 1995

In this paper, $TiO_{2}-V_{2}O_{5}$ humidity sensors are fabricated by Sol-Gel method. For the establishment of optimum processing condition which is good humidity sensitive characteristics for specimens, their microstructures and crystalline-structures are analysed. Grain size increases with substitution rate of $V^{5+}$ on $Ti^{4+}$ site. From the analysis of XRD, $V^{5+}$ peak can't confirm with $V_{2}O_{5}$ rate. Their humidity sensitive characteristics is good at 1mol% of $V_{2}O_{5}$ rate and heat-treated at $700^{\circ}C$. The capacitance of specimens decreases with frequency.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.4
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• pp.294-299
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• 2000

For practical application as a humidity sensor SnO$_2$thick films devices were fabricated on the refresh type electrode by screen printing method and their material and humidity sensing properties were investigated. As a function of Sb$_{2}$/O$_{3}$ addition rate grain size was increased while porosity and initial resistance were rapidly decreased. And the area of resistance variation according to relative humidity was decreased with increasing heat treatment temperature. SnO$_2$thick film device heat treated at 95$0^{\circ}C$ and contained 0.05mole% Sb$_{2}$/O$_{3}$ had a best humidity sensing properties. From this result it is conformed that humidity sensing properties of SnO$_2$thick film devices could be approved by very small amount of Sb$_{2}$/O$_{3}$ addition.

• Journal of Sensor Science and Technology
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• v.23 no.1
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• pp.42-45
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• 2014

Recently, tremendous application utilizing electrospun nanofibers have been actively reported due to its several advantages, such as high surface to volume ratio, simple fabrication and high-throughput manufacturing. In this paper, we developed highly sensitive and consistent nanofiber humidity sensor by electrospinning. The humidity sensor was fabricated by rapid electrospinning (~2 sec) $TiO_2$/PVP/LiCl mixed solution on the micro-interdigitated electrode. In order to evaluate the humidity sensing performances, we measured current response using DC bias voltage under various relative humidity levels. The results show fast response / recovery time and marginal hysteresis as well as long-term stability. In addition, with the aid of micro-interdigitated electrode, we can reduce a total resistance of the sensor and increase the total reaction area of nanofibers across the electrodes resulting in high sensitivity and enhanced current level. Therefore, we expect that the electrospun nanofiber array for humidity sensor can be feasible and promising for diverse humidity sensing application.

• Journal of the Korean Ceramic Society
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• v.36 no.5
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• pp.465-470
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• 1999

Sensing properties of $\alpha$-Fe2O3 thin film to reducing gases such as CHx and CO were systematically examined after deposition on Al2O3 substrate by PECVD(Plasma Enhanced Chemical Vapor Deposition)technique. Microstructure of deposited $\alpha$-Fe2O3 thin film showed the porous island structure. This specimen was annealed at 450, 550, $650^{\circ}C$ to enhance the gas sensing properties and investigated in terms of CO and C4H10 concentration from 500ppm to 3,000 ppm at operating temperature of 35$0^{\circ}C$ The gas sensitivity(%) to C4H10 measured at the operating temperature of 35$0^{\circ}C$ was 98.24 (highest sensitivity) 69.51 to CO and 2% to CH4 respectviely.

• Journal of Sensor Science and Technology
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• v.20 no.6
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• pp.428-433
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• 2011

We report on the building of a micro sensor array based on typical semiconductor fabrication processes aimed at monitoring selectively a specific gas in ambient of other gases. Chemical sensors can be applied for an electronic nose and/or robots using this technique. Microsensor array was fabricated on the same chip using 0.6${\mu}m$ CMOS technology, and unique gas sensing patterns were obtained by principal component analysis from the array. $SnO_2$/Pt sensor for CO gas showed a high selectivity to buthane gas and humidity. $SnO_2$ sensor for hydrogen gas, however, showed a low selectivity to CO and buthane gas. We can obtain more distinguishable patterns that provide the small sensing deviation(the high seletivity) toward a given analyte in the response space than in the chemical space through the specific parameterization of raw data for chemical image formation.

• Journal of Sensor Science and Technology
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• v.17 no.5
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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.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.3
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• pp.705-711
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• 2000

A thin film oxide semiconductor micro gas sensor array which shows only 60 mW of power consumption at an operating temperature of $300^{\circ}C$ has been fabricated using microfabrication and micromachining techniques. Excellent thermal insulation of the membrane is achieved by the use of a double-layer structure of $0.1\mum\; thick\; Si_3N_4 \;and\; 1 \mum$ thick phosphosilicate glass (PSG) prepared by low-pressure chemical-vapor deposition (LPCVD) and atmospheric-pressure chemical-vapor deposition (APCVD), respectively. The sensor array consists of such thin film oxide semiconductor sensing materials as 1 wt.% Pd-doped $SnO_2,\; 6 wt.% A1_2O_3-doped\; ZnO,\; WO_3$/ and ZnO. Baseline resistances of the four sensing materials were found to be stable after the aging for three days at $300^{\circ}C$. The thin film oxide semiconductor micro gas sensor array exhibited resistance changes usable for subsequent data processing upon exposure to various gases and the sensitivity strongly depended on the sensing layer materials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.3
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• pp.228-233
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• 2007

Core technologies for integrating hydrogen gas sensor were investigated. In this study, the thermally isolated micro-hot-plate with areas of $100{\times}100-260{\times}260{\mu}m^2$ was fabricated by utilizing surface micromachining technique that provides better manufacturing yield than bulk micromachining counterpart. The optimum design of the sensor was peformed by analyzing the thermal profile of the structure obtained from a ANSYS simulator. The 400-nm-thick polysilicon films doped with phosphorus, the 300-nm-thick aluminum films, and the 200-nm-thick $SnO_2$(or ZnO)films were used as the micro-heater material, the temperature sensor material, and the gas sensitive material, respectively. The experimental results show that the developed gas sensors can detect $H_2$ concentration as low as 1 ppm.