• Title/Summary/Keyword: Metal Oxide sensors

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Synthesis and Characterization of Zinc Oxide Nanorods for Nitrogen Dioxide Gas Detection

  • Park, Jong-Hyun;Kim, Hyojin
    • Journal of the Korean institute of surface engineering
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    • v.54 no.5
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    • pp.260-266
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    • 2021
  • Synthesizing low-dimensional structures of oxide semiconductors is a promising approach to fabricate highly efficient gas sensors by means of possible enhancement in surface-to-volume ratios of their sensing materials. In this work, vertically aligned zinc oxide (ZnO) nanorods are successfully synthesized on a transparent glass substrate via seed-mediated hydrothermal synthesis method with the use of a ZnO nanoparticle seed layer, which is formed by thermally oxidizing a sputtered Zn metal film. Structural and optical characterization by x-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy reveals the successful preparation of the ZnO nanorods array of the single hexagonal wurtzite crystalline phase. From gas sensing measurements for the nitrogen dioxide (NO2) gas, the vertically aligned ZnO nanorod array is observed to have a highly responsive sensitivity to NO2 gas at relatively low concentrations and operating temperatures, especially showing a high maximum sensitivity to NO2 at 250 ℃ and a low NO2 detection limit of 5 ppm in dry air. These results along with a facile fabrication process demonstrate that the ZnO nanorods synthesized on a transparent glass substrate are very promising for low-cost and high-performance NO2 gas sensors.

Vertically aligned cupric oxide nanorods for nitrogen monoxide gas detection

  • Jong-Hyun Park;Hyojin Kim
    • Journal of the Korean institute of surface engineering
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    • v.56 no.4
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    • pp.219-226
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    • 2023
  • Utilizing low-dimensional structures of oxide semiconductors is a promising approach to fabricate relevant gas sensors by means of potential enhancement in surface-to-volume ratios of their sensing materials. In this work, vertically aligned cupric oxide (CuO) nanorods are successfully synthesized on a transparent glass substrate via seed-mediated hydrothermal synthesis method with the use of a CuO nanoparticle seed layer, which is formed by thermally oxidizing a sputtered Cu metal film. Structural and optical characterization by x-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy reveals the successful preparation of the CuO nanorods array of the single monoclinic tenorite crystalline phase. From gas sensing measurements for the nitrogen monoxide (NO) gas, the vertically aligned CuO nanorod array is observed to have a highly responsive sensitivity to NO gas at relatively low concentrations and operating temperatures, especially showing a high maximum sensitivity to NO at 200 ℃ and a low NO detection limit of 2 ppm in dry air. These results along with a facile fabrication process demonstrate that the CuO nanorods synthesized on a transparent glass substrate are very promising for low-cost and high-performance NO gas sensors.

High-sensitivity ZnO gas Sensor with a Sol-gel-processed SnO2 Seed Layer (Sol-Gel 방법으로 제작된 SnO2 seed layer를 적용한 고반응성 ZnO 가스 센서)

  • Kim, Sangwoo;Bak, So-Young;Han, Tae Hee;Lee, Se-Hyeong;Han, Ye-ji;Yi, Moonsuk
    • Journal of Sensor Science and Technology
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    • v.29 no.6
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    • pp.420-426
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    • 2020
  • A metal oxide semiconductor gas sensor is operated by measuring the changes in resistance that occur on the surface of nanostructures for gas detection. ZnO, which is an n-type metal oxide semiconductor, is widely used as a gas sensor material owing to its high sensitivity. Various ZnO nanostructures in gas sensors have been studied with the aim of improving surface reactions. In the present study, the sol-gel and vapor phase growth techniques were used to fabricate nanostructures to improve the sensitivity, response, and recovery rate for gas sensing. The sol-gel method was used to synthesize SnO2 nanoparticles, which were used as the seed layer. The nanoparticles size was controlled by regulating the process parameters of the solution, such as the pH of the solution, the type and amount of solvent. As a result, the SnO2 seed layer suppressed the aggregation of the nanostructures, thereby interrupting gas diffusion. The ZnO nanostructures with a sol-gel processed SnO2 seed layer had larger specific surface area and high sensitivity. The gas response and recovery rate were 1-7 min faster than the gas sensor without the sol-gel process. The gas response increased 4-24 times compared to that of the gas sensor without the sol-gel method.

Extension of the Dynamic Range using the Switching Operation of In-Pixel Inverter in Complementary Metal Oxide Semiconductor Image Sensors

  • Seong, Donghyun;Choi, Byoung-Soo;Kim, Sang-Hwan;Lee, Jimin;Lee, Jewon;Lee, Junwoo;Shin, Jang-Kyoo
    • Journal of Sensor Science and Technology
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    • v.28 no.2
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    • pp.71-75
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    • 2019
  • This paper proposes the extension of the dynamic range in complementary metal oxide semiconductor (CMOS) image sensors (CIS) using switching operation of in-pixel inverter. A CMOS inverter is integrated in each unit pixel of the proposed CIS for switching operations. The n+/p-substrate photodiode junction capacitances are added to each unit pixel. When the output voltage of the photodiode is less than half of the power supply voltage of the CMOS inverter, the output voltage of the CMOS inverter changes from 0 V to the power supply voltage. Hence, the output voltage of the CMOS inverter is adjusted by changing the supply voltage of the CMOS inverter. Thus, the switching point is adjusted according to light intensity when the supply voltage of the CMOS inverter changes. Switching operations are then performed because the CMOS inverter is integrated with in each unit pixel. The proposed CIS is composed of a pixel array, multiplexers, shift registers, and biasing circuits. The size of the proposed pixel is $10{\mu}m{\times}10{\mu}m$. The number of pixels is $150(H){\times}220(V)$. The proposed CIS was fabricated using a $0.18{\mu}m$ 1-poly 6-metal CMOS standard process and its characteristics were experimentally analyzed.

Peculiarities of gas sensing characteristics of SnO2-based sensors modified by SnO2-Au nanocomposites synthesized by SILD method

  • Korotcenkov, Ghenadii;Cho, Beong-Ki;Tolstoy, Valery;Gulina, Larisa B.;Han, Sang-Do
    • Journal of Sensor Science and Technology
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    • v.18 no.6
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    • pp.417-422
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    • 2009
  • The problems associated with the synthesis, characterization and application of $SnO_2$-Au nanocomposites for the optimization of conductometric gas sensors have been discussed in this report. Nanocomposites have been synthesized on the surface of $SnO_2$ films using successive ionic layer deposition(SILD) method. It has been shown that the proposed approach to surface modification of metal oxide films is an excellent method for the optimization of the operating characteristics of $SnO_2$-based gas sensors, being developed for the detection of reducing gases as well as ozone.

Electrochemical Properties of a Si3N4 Dielectric Layer Deposited on Anodic Aluminum Oxide for Chemical Sensors

  • Jo, Ye-Won;Lee, Sung-Gap;Yeo, Jin-Ho;Lee, Dong-Jin
    • Transactions on Electrical and Electronic Materials
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    • v.17 no.3
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    • pp.159-162
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    • 2016
  • We studied an electrolyte-dielectric metal (EDM) device based on a Si3N4 layer-coated anodic aluminium oxide (AAO) template for chemical sensors. The AAO templates were fabricated using a two-step anodization procedure at 0℃ and 70 V in 0.3 M oxalic acid, after which the Si3N4 was deposited on them using plasma enhanced chemical vapor deposition (PECVD). The average pore size was approximately 106 nm and the depth of the AAO templates was 24.6 nm to 86.5 nm. The Si3N4 layer-coated AAO is more stable than a single AAO template.

Effect on the Sensitivity of a Hydrogen Sensor by Pd Electrode Patterns at High Temperature (고온에서 Pd 전극의 형태가 수소 센서의 감도에 미치는 영향)

  • Kim, Seong-Jeen
    • Journal of IKEEE
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    • v.22 no.2
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    • pp.356-361
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    • 2018
  • We investigated a hydrogen gas sensor which is available in a high temperature atmosphere. The hydrogen sensors were fabricated into a metal-oxide-semiconductor (MOS) structure made of $Pd/Ta_2O_5/SiC$, and the thin tantalum oxide ($Ta_2O_5$) layer was fabricated by rapid thermal oxidation (RTO). In the experiment, we made three types of sensors with different palladium (Pd) patterns to evaluate the effect of Pd electrode on response characteristics. As the result, the response characteristics in capacitance were improved further when the filled area of the Pd electrode became larger.

Design and performance evaluation of portable electronic nose systems for freshness evaluation of meats (육류 신선도 판별을 위한 휴대용 전자코 시스템 설계 및 성능 평가)

  • Kim, Jae-Gone;Cho, Byoung-Kwan
    • Korean Journal of Agricultural Science
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    • v.38 no.3
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    • pp.525-532
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    • 2011
  • The aim of this study was to develop a portable electronic nose system for freshness measurement of meats, which could be an alterative of subjective measurements of human nose and time-consuming measurements of conventional gas chromatograph methods. The portable electronic system was o optimized by comparing the measurement sensitivity and hardware efficiency, such as power consumption and dimension reduction throughout two stages of the prototypes. The electronic nose systems were constructed using an array of four different metal oxide semiconductor sensors. Two different configurations of sensor array with dimension were designed and compared the performance respectively. The final prototype of the system showed much improved performance on saving power consumption and dimension reduction without decrease of measurement sensitivity of pork freshness. The results show the potential of constructing a portable electronic system for the measurement of meat quality with high sensitivity and energy efficiency.

CMOS Binary Image Sensor Using Double-Tail Comparator with High-Speed and Low-Power Consumption

  • Kwen, Hyeunwoo;Jang, Junyoung;Choi, Pyung;Shin, Jang-Kyoo
    • Journal of Sensor Science and Technology
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    • v.30 no.2
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    • pp.82-87
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    • 2021
  • In this paper, we propose a high-speed, low-power complementary metal-oxide semiconductor (CMOS) binary image sensor featuring a gate/body-tied (GBT) p-channel metal-oxide-semiconductor field-effect transistor (PMOSFET)-type photodetector based on a double-tail comparator. The GBT photodetector forms a structure in which the floating gate (n+ polysilicon) and body of the PMOSFET are tied, and amplifies the photocurrent generated by incident light. The double-tail comparator compares the output signal of a pixel against a reference voltage and returns a binary signal, and it exhibits improved power consumption and processing speed compared with those of a conventional two-stage comparator. The proposed sensor has the advantages of a high signal processing speed and low power consumption. The proposed CMOS binary image sensor was designed and fabricated using a standard 0.18 ㎛ CMOS process.

Photocurrent Characteristics of Gate/Body-Tied MOSFET-Type Photodetector with High Sensitivity

  • Jang, Juneyoung;Choi, Pyung;Lyu, Hong-Kun;Shin, Jang-Kyoo
    • Journal of Sensor Science and Technology
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    • v.31 no.1
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    • pp.1-5
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    • 2022
  • In this paper, the photocurrent characteristics of gate/body-tied (GBT) metal-oxide semiconductor field-effect transistor (MOSFET)-type photodetector with high sensitivity in the 408 nm - 941 nm range are presented. High sensitivity is important for photodetectors, which are used in several scientific and industrial applications. Owing to its inherent amplifying characteristics, the GBT MOSFET-type photodetector exhibits high sensitivity. The presented GBT MOSFET-type photodetector was designed and fabricated via a standard 0.18 ㎛ complementary metal-oxide-semiconductor (CMOS) process, and its characteristics were analyzed. The photodetector was analyzed with respect to its width to length (W/L) ratio, bias voltage, and incident-light wavelength. It was confirmed experimentally that the presented GBT MOSFET-type photodetector has over 100 times higher sensitivity than a PN-junction photodiode with the same area in the 408 nm - 941 nm range.