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Optimization of Nanocrystalline Metal Oxides-based Gas Sensors for Hydrogen Detection

Niroula, Prakash
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1659703425479053

Abstract Details

2022, Master of Science, University of Toledo, Mechanical Engineering.
A large amount of living and industrial waste gases is released into the environment every day. Monitoring and control of such environmental gases and industrial emissions are key targets for many domestic activities and industrial applications. The development of high-performance gas sensors is therefore crucial for the detection of those hazardous gases and to keep them under control. Decades of research and development have proven metal oxides to be the potential materials for gas sensor application owing to their high stability, high sensitivity, and outstanding ability to detect a wide range of target gases. However, challenges remain inevitable when it comes to overall sensing performance based on selectivity, response time, recovery time, and operating temperature requirements. Therefore, optimization of the existing metal oxide gas sensors by different techniques is important. In this study, possible attempts to enhance the performance of zinc oxide (ZnO) and nickel oxide (NiO) based gas sensors by impurity doping and incorporating heterostructures were investigated. Zinc oxide is an n-type semiconductor with a wide bandgap of 3.37 eV, large excitation binding energy of 60 meV. Therefore, it is considered one of the most promising semiconductor materials for gas sensor applications. With thermal activation, we can obtain more carriers on the surface of ZnO at high temperatures and increase the effective adsorption sites on the surface, thus increasing the adsorption. Doping with impurity elements is one of the best ways to enhance the sensing performance of ZnO. Iron-doped zinc oxide thin films were prepared via the sol-gel process and the effects of dopant on the microstructure, surface morphology, electrical properties, and gas sensitivity of ZnO were investigated. The optimum gas sensing performance was obtained from 6.0 at.% Fe-doped ZnO sample at 250 °C. Similarly, nitrogen-doped zinc oxide thin films were fabricated through radio frequency (rf) magnetron sputtering coating. The effects of N-doping were investigated which showed that the 3.0 vol. % N-doped ZnO films exhibited a better sensing performance and crystallinity compared to the undoped ZnO films. NiO/ZnO bilayer heterostructure thin films were also fabricated via combined sol-gel spin coating and rf-magnetron sputtering. The gas sensing response of this heterostructure showed a high sensitivity than pure NiO thin films and the optimum performance was obtained at 150 °C. The NiO/ZnO bilayer heterostructure thin film also exhibited better selectivity for H2 than CH4. Lastly, nickel oxide thin films were fabricated via sol-gel spin coating using different concentrations of Triton X-100 to analyze its effects which suggested that the Triton had a desirable influence on gas sensing properties of NiO thin films. The incorporation of these surface modification techniques for optimization of metal oxides-based gas sensors demonstrated an improved performance for hydrogen detection.
Ahalapitiya Jayatissa, Dr. (Advisor)
120 p.
Mechanical Engineering
Thin films, zinc oxide, nickel oxide, gas sensors, Fe-doped ZnO, N-doped ZnO

Recommended Citations

Citations

  • Niroula, P. (2022). Optimization of Nanocrystalline Metal Oxides-based Gas Sensors for Hydrogen Detection [Master's thesis, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1659703425479053

    APA Style (7th edition)

  • Niroula, Prakash. Optimization of Nanocrystalline Metal Oxides-based Gas Sensors for Hydrogen Detection. 2022. University of Toledo, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1659703425479053.

    MLA Style (8th edition)

  • Niroula, Prakash. "Optimization of Nanocrystalline Metal Oxides-based Gas Sensors for Hydrogen Detection." Master's thesis, University of Toledo, 2022. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1659703425479053

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Toledo and OhioLINK.