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Surface Passivation Effect on CO2 Sensitivity of Spray Pyrolysis Deposited Pd-F: SnO2 Thin Film Gas Sensor

Received: 12 September 2014     Accepted: 27 September 2014     Published: 10 October 2014
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Abstract

Different thin films samples made of SnO2, F:SnO2, Pd: SnO2 and and co-doped Pd-F: SnO2 were deposited at a substrate temperature of 450oC using optimized doping concentrations of F and Pd, thereafter the samples were annealed and passivated in a tube furnace at 450oC. Optical and electrical methods were used in characterizing the thin film samples: The band gap energy for all samples was extracted from optical data using a proprietary software, Scout™ 98. The calculated band gap energy were found to be 4.1135eV for Pd:SnO2 and 3.8014eV for F:SnO2 being the highest and the lowest calculated band gap energies, respectively. The wide band gap energy has been attributed to the incorporation of Pd ions in crystal lattice of SnO2 thin film for Pd:SnO2 while for F:SnO2 has been due to incorporation of F- ions in the crystal lattice of SnO2 which gives rise to donor levels in the SnO2 band gap. This causes the conduction band to lengthen resulting to a reduction in the band gap energy value. The electrical resistivity was done by measuring the sheet resistance of the SnO2, Pd:SnO2, F:SnO2 and Pd-F:SnO2 thin films. The undoped SnO2 thin film had the highest sheet resistivity of 0.5992 Ωcm while F:SnO2 had the lowest sheet resistivity of 0.0075 Ωcm. The low resistivity of F:SnO2 results from substitution incorporation of F- ions in the crystal lattice of SnO2 thin films, instead of O- ions which lead to an increase in free carrier concentration. The Pd-F:SnO2 gas sensor device was tested for CO2 gas sensing ability using a lab assembled gas sensing unit. The performance of the gas sensor device was observed that: the as prepared device was more sensitive to CO2 gas than those subjected to annealing and passivation. The decrease in the sensitivity of the annealed Pd-F: SnO2 gas sensor is attributed to decrease in grain boundary potential resulting from grain growth. This causes a decrement in adsorption properties of CO- and O- species by the annealed Pd-F: SnO2 thin film. The sensitivity of passivated Pd-F: SnO2 gas sensor was found to be the lowest. The low sensitivity is due to the effects of nitration and decrement in grain boundary potential resulting from grain growth, nevertheless, the sensitivity of the passivated Pd-F: SnO2 thin film was found to be within the range for gas sensing applications.

Published in Advances in Materials (Volume 3, Issue 5)
DOI 10.11648/j.am.20140305.12
Page(s) 38-44
Creative Commons

This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.

Copyright

Copyright © The Author(s), 2014. Published by Science Publishing Group

Keywords

Spray Pyrolysis, Fluorine doping, Palladium doping, co-doping, Palladium and Fluorine co-doping, Annealing, Passivation, F -co- doped Pd:SnO2 (Pd-F: SnO2)

References
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    Patrick Mwinzi Mwathe, Robinson Musembi, Mathew Munji, Benjamin Odari, Lawrence Munguti, et al. (2014). Surface Passivation Effect on CO2 Sensitivity of Spray Pyrolysis Deposited Pd-F: SnO2 Thin Film Gas Sensor. Advances in Materials, 3(5), 38-44. https://doi.org/10.11648/j.am.20140305.12

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    Patrick Mwinzi Mwathe; Robinson Musembi; Mathew Munji; Benjamin Odari; Lawrence Munguti, et al. Surface Passivation Effect on CO2 Sensitivity of Spray Pyrolysis Deposited Pd-F: SnO2 Thin Film Gas Sensor. Adv. Mater. 2014, 3(5), 38-44. doi: 10.11648/j.am.20140305.12

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    AMA Style

    Patrick Mwinzi Mwathe, Robinson Musembi, Mathew Munji, Benjamin Odari, Lawrence Munguti, et al. Surface Passivation Effect on CO2 Sensitivity of Spray Pyrolysis Deposited Pd-F: SnO2 Thin Film Gas Sensor. Adv Mater. 2014;3(5):38-44. doi: 10.11648/j.am.20140305.12

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  • @article{10.11648/j.am.20140305.12,
      author = {Patrick Mwinzi Mwathe and Robinson Musembi and Mathew Munji and Benjamin Odari and Lawrence Munguti and Alex Alfred Ntilakigwa and Julius Mwabora and Walter Njoroge and Bernard Aduda and Boniface Muthoka},
      title = {Surface Passivation Effect on CO2 Sensitivity of Spray Pyrolysis Deposited Pd-F: SnO2 Thin Film Gas Sensor},
      journal = {Advances in Materials},
      volume = {3},
      number = {5},
      pages = {38-44},
      doi = {10.11648/j.am.20140305.12},
      url = {https://doi.org/10.11648/j.am.20140305.12},
      eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.am.20140305.12},
      abstract = {Different thin films samples made of SnO2, F:SnO2, Pd: SnO2 and and co-doped Pd-F: SnO2 were deposited at a substrate temperature of 450oC using optimized doping concentrations of F and Pd, thereafter the samples were annealed and passivated in a tube furnace at 450oC. Optical and electrical methods were used in characterizing the thin film samples: The band gap energy for all samples was extracted from optical data using a proprietary software, Scout™ 98. The calculated band gap energy were found to be 4.1135eV for Pd:SnO2 and 3.8014eV for F:SnO2 being the highest and the lowest calculated band gap energies, respectively. The wide band gap energy has been attributed to the incorporation of Pd ions in crystal lattice of SnO2 thin film for Pd:SnO2 while for F:SnO2 has been due to incorporation of F- ions in the crystal lattice of SnO2 which gives rise to donor levels in the SnO2 band gap. This causes the conduction band to lengthen resulting to a reduction in the band gap energy value.  The electrical resistivity was done by measuring the sheet resistance of the SnO2, Pd:SnO2, F:SnO2 and Pd-F:SnO2 thin films. The undoped SnO2 thin film had the highest sheet resistivity of 0.5992 Ωcm while F:SnO2 had the lowest sheet resistivity of 0.0075 Ωcm. The low resistivity of F:SnO2 results from substitution incorporation of F- ions in the crystal lattice of SnO2 thin films, instead of O- ions which lead to an increase in free carrier concentration. The Pd-F:SnO2 gas sensor device was tested for CO2 gas sensing ability using a lab assembled gas sensing unit. The performance of the gas sensor device was observed that: the as prepared device was more sensitive to CO2 gas than those subjected to annealing and passivation. The decrease in the sensitivity of the annealed Pd-F: SnO2 gas sensor is attributed to decrease in grain boundary potential resulting from grain growth.  This causes a decrement in adsorption properties of CO- and O- species by the annealed Pd-F: SnO2 thin film. The sensitivity of passivated Pd-F: SnO2 gas sensor was found to be the lowest. The low sensitivity is due to the effects of nitration and decrement in grain boundary potential resulting from grain growth, nevertheless, the sensitivity of the passivated Pd-F: SnO2 thin film was found to be within the range for gas sensing applications.},
     year = {2014}
    }
    

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  • TY  - JOUR
    T1  - Surface Passivation Effect on CO2 Sensitivity of Spray Pyrolysis Deposited Pd-F: SnO2 Thin Film Gas Sensor
    AU  - Patrick Mwinzi Mwathe
    AU  - Robinson Musembi
    AU  - Mathew Munji
    AU  - Benjamin Odari
    AU  - Lawrence Munguti
    AU  - Alex Alfred Ntilakigwa
    AU  - Julius Mwabora
    AU  - Walter Njoroge
    AU  - Bernard Aduda
    AU  - Boniface Muthoka
    Y1  - 2014/10/10
    PY  - 2014
    N1  - https://doi.org/10.11648/j.am.20140305.12
    DO  - 10.11648/j.am.20140305.12
    T2  - Advances in Materials
    JF  - Advances in Materials
    JO  - Advances in Materials
    SP  - 38
    EP  - 44
    PB  - Science Publishing Group
    SN  - 2327-252X
    UR  - https://doi.org/10.11648/j.am.20140305.12
    AB  - Different thin films samples made of SnO2, F:SnO2, Pd: SnO2 and and co-doped Pd-F: SnO2 were deposited at a substrate temperature of 450oC using optimized doping concentrations of F and Pd, thereafter the samples were annealed and passivated in a tube furnace at 450oC. Optical and electrical methods were used in characterizing the thin film samples: The band gap energy for all samples was extracted from optical data using a proprietary software, Scout™ 98. The calculated band gap energy were found to be 4.1135eV for Pd:SnO2 and 3.8014eV for F:SnO2 being the highest and the lowest calculated band gap energies, respectively. The wide band gap energy has been attributed to the incorporation of Pd ions in crystal lattice of SnO2 thin film for Pd:SnO2 while for F:SnO2 has been due to incorporation of F- ions in the crystal lattice of SnO2 which gives rise to donor levels in the SnO2 band gap. This causes the conduction band to lengthen resulting to a reduction in the band gap energy value.  The electrical resistivity was done by measuring the sheet resistance of the SnO2, Pd:SnO2, F:SnO2 and Pd-F:SnO2 thin films. The undoped SnO2 thin film had the highest sheet resistivity of 0.5992 Ωcm while F:SnO2 had the lowest sheet resistivity of 0.0075 Ωcm. The low resistivity of F:SnO2 results from substitution incorporation of F- ions in the crystal lattice of SnO2 thin films, instead of O- ions which lead to an increase in free carrier concentration. The Pd-F:SnO2 gas sensor device was tested for CO2 gas sensing ability using a lab assembled gas sensing unit. The performance of the gas sensor device was observed that: the as prepared device was more sensitive to CO2 gas than those subjected to annealing and passivation. The decrease in the sensitivity of the annealed Pd-F: SnO2 gas sensor is attributed to decrease in grain boundary potential resulting from grain growth.  This causes a decrement in adsorption properties of CO- and O- species by the annealed Pd-F: SnO2 thin film. The sensitivity of passivated Pd-F: SnO2 gas sensor was found to be the lowest. The low sensitivity is due to the effects of nitration and decrement in grain boundary potential resulting from grain growth, nevertheless, the sensitivity of the passivated Pd-F: SnO2 thin film was found to be within the range for gas sensing applications.
    VL  - 3
    IS  - 5
    ER  - 

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Author Information
  • Department of Physics, Kenyatta University, Nairobi, Kenya

  • Department of Physics, University of Nairobi, Nairobi, Kenya

  • Department of Physics, Kenyatta University, Nairobi, Kenya

  • Department of Physics, University of Nairobi, Nairobi, Kenya

  • Department of Physics, Kenyatta University, Nairobi, Kenya

  • Department of Physics, University of Nairobi, Nairobi, Kenya

  • Department of Physics, University of Nairobi, Nairobi, Kenya

  • Department of Physics, Kenyatta University, Nairobi, Kenya

  • Department of Physics, University of Nairobi, Nairobi, Kenya

  • Department of Physics, University of Nairobi, Nairobi, Kenya

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