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Author: search.filters.author.Hazra, ArnabSubject: search.filters.subject.Electrochemical oxidation

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    Studies on Hydrogen Sensing by Anodized Nanoporous Titania Thin Film Using Soft Drink Electrolyte
    (SEI Publisher, 2013-04) Hazra, Arnab
    Nano-porous titanium dioxide (TiO2) thin films were developed by UV assisted potentiostatic anodization of 99.7% pure titanium foil. The internationally popular soft drink 􀈁Coca-Cola􀈂 was used as the electrolyte in this anodization process. Electrochemical oxidation and photoetching were carried out at room temperature and at 10 V potentiostatic bias without and with 400 W UV light illumination respectively. The prepared TiO2 thin film was annealed at 150ᴼC for 3 hours. The surface of the prepared TiO2 film was characterized with Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) to confirm the crystallinity, porous structure and surface roughness. The Optical study revealed a band gap of 3.898 eV. Hot probe method exhibited n-type conductivity of the electrochemically grown TiO2 thin films. Palladium-Silver alloy (Pd-Ag) contacts were deposited laterally on the oxide surface as catalytic metal electrodes to fabricate a planar sensor configuration. The hydrogen sensor study was carried out at different temperatures (100 to 200ᴼC) and in different hydrogen gas concentrations (1000 to 10000 ppm). Nanocrystalline and nano-porous TiO2 sensor was promising to sense hydrogen in air ambient with relatively fast response and recovery times (e.g. ~2.9 s and ~75 s) at the optimum temperature of 1500C. Brief mechanism behind the sensing performance has been also discussed.
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    Anodically grown nanocrystalline titania thin film for hydrogen gas sensors – a comparative study of planar and MAIM configuration
    (Elsevier, 2013-11) Hazra, Arnab
    Nanocrystalline titanium dioxide (TiO2) thin film was grown by UV assisted anodization of 0.25 mm thick titanium foil (99.7% pure). Room temperature electrochemical oxidation and photo etching were carried out in 0.1 M dilute H2SO4 electrolyte and at 10 V potentiostatic bias without and with 400 W UV light illumination respectively. While 2D-XRD confirmed the anatase crystalline feature AFM study revealed a rough morphology. A band gap of 3.35 eV was determined by optical study. Palladium (Pd) contacts were deposited laterally on the oxide surface as catalytic metal electrodes to fabricate a planar sensor configuration and a vertical metal-active insulator-metal (MAIM) structure was configured using palladium and titanium-silver alloy as top and bottom electrode respectively. The hydrogen sensor study was carried out at different temperatures (100–175 °C) and with different gas concentrations (0.1–1%) for both planar and MAIM structures in nitrogen as well as in air. A detailed hydrogen gas response characteristic was studied for these two types of sensor structures. Both the sensor structures were found suitable to sense 1% hydrogen in nitrogen ambient and at the optimum temperature of 150 °C with a pretty fast response time of 1.1 s for planar sensor and 1.4 s for MAIM sensor. However, the corresponding recovery time of 102.5 s and 92.3 s were quite long. The subsequent studies in air in the identical conditions recorded the response time and recovery time of 0.49 s and 28.8 s for planar and 1.5 s and 44.6 s for MAIM configurations respectively. The selectivity and the long term stability were investigated. A comparative sensor study with the two devices was performed and the results have been explained.