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Author: search.filters.author.Pengpad, PuttaponSubject: search.filters.subject.graphene oxide

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    Sensing layer combination of vertically aligned ZnO nanorods and graphene oxide for ultrahigh sensitivity IDE capacitive humidity sensor
    (2020-06-01)
    Pongampai, Satana
    ;
    Pengpad, Puttapon
    ;
    Meananeatra, Rattanawan
    ;
    Chaisriratanakul, Woraphan
    ;
    Poyai, Amporn
    An interdigitated electrode (IDE) capacitive humidity sensor fabricated on a silicon substrate was used to investigate sensing materials, which proved to be an ultrahigh-sensitivity humidity sensor. A sensing layer combination (SLC) between vertically aligned ZnO nanorods and optimal graphene oxide (GO) was prepared on the device and was tested as a humidity sensor. X-ray diffractometry (XRD) exhibited crystallized wurtzite structure of ZnO nanorods and transmission electron microscope (TEM) shown perfectly indexed hexagonal wurtzite ZnO structure dots position correspondence. A scanning electron microscope (SEM) was used to analyze ZnO nanorods/GO morphologies. Furthermore, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) clearly exhibited GO presence and hydrophilic functional groups (carboxyl, epoxy, and hydroxyl), respectively. The SLC prominently demonstrated ultrahigh sensitivity (up to 196.95% or 1.97 times from commercial sensor; HS1101, Humirel) and linear responses behavior with 0.96 for coefficient of determination. The device sensitivity obviously improved as steps of 40, 50, 60, 70, 80, and 90% RH at values of 1.09, 1.41, 1.51, 1.65, 1.80, and 1.91 times, respectively. The device also exhibited fast response (25 s) and short recovery times (17 s). Its hysteresis (6.58%) manifestly improved to 1.84 times. Moreover, repeatability and long-term ability of the device demonstrated high accuracy (range ±0.37pF) and durability. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
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    Study of Nitride Thickness on Sensitivity IDEs Humidity Sensor Based on Graphene Oxide Sensing
    (2020-03-01)
    Pongampai, Satana
    ;
    Pengpad, Puttapon
    ;
    Meananeatra, Rattanawan
    ;
    Atiwongsangthong, Narin
    ;
    Muanghlua, Rangson
    An interdigitaged electrodes (IDEs) humidity sensor was patterned like a combs by lithography process based on silicon bulk substrate with different nitride thickness (50, 100 and 150 nm). This research studied an effect of thick nitride on sensitivity of IDEs humidity sensor based APTES adhesive layer with graphene oxide (GO) sensing material. The IDEs humidity sensor based on GO was comparatively examined all thick nitride conditions. Capacitance value of fresh IDEs humidity sensor shown not significant change all nitride thickness but it affected to sensitivity after GO coating due to high GO densified onto IDEs surface. Scanning Electron Microscope (SEM) was analyzed GO distribution and surface morphology. Raman spectroscopy clearly revealed the GO presence. The sensitivity from 50 to 80 %RH for optimal 100 nm thick nitride shows improvement to 2.78 and 1.27 times or 278.35% and 127.46% based on 50 and 150 nm thick nitride, respectively. Furthermore, the optimal condition of IDEs humidity sensor shows a little response and recovery times (11 and 7 sec), low hysteresis (3.21%), fine repeatability as well as high accuracy on long-term ability test. It clearly demonstrated for high sensitivity of nitride IDEs humidity sensor based on GO sensing film deposition.