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    High Quality Zinc Oxide Thin films and Nanostructures Prepared by Pulsed Laser Deposition for Photodetectors

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    Tahani Flemban - Dissertation - Final Draft.pdf
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    Type
    Dissertation
    Authors
    Flemban, Tahani H. cc
    Advisors
    Roqan, Iman S. cc
    Committee members
    Li, Lain-Jong cc
    Rothenberger, Alexander
    Al-Dossari, Omar
    Program
    Materials Science and Engineering
    KAUST Department
    Physical Science and Engineering (PSE) Division
    Date
    2017-12-11
    Permanent link to this record
    http://hdl.handle.net/10754/626351
    
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    Abstract
    Zinc oxide (ZnO) semiconductors have been utilized by many researchers, due to its unique properties beneficial for functional devices. In particular, gadolinium (Gd)–doped ZnO exhibits high ferromagnetic and electrical properties, which is attributed to defect/impurity bands mediated by Gd dopants. In this dissertation, I study the effects of Gd concentration, oxygen pressure using pulsed laser deposition (PLD), and thermal annealing on the optical and structural properties of undoped and Gd-doped ZnO films and nanostructures. Moreover, as the growth of practical ZnO nanostructures-based devices without catalyst, while presently challenging, is highly important for many applications. Thus, for the first time, a novel method is developed for growing well aligned ZnO nanorods (NRs) by optimizing PLD conditions using Gd-doped ZnO target without any catalyst in a single step. This study shows that, both the lattice orientation of the substrate and the Gd characteristics are significant in enhancing the NR growth. Our findings reveal that precise control of the NR density can be achieved by changing the oxygen partial pressure. Furthermore, due to the Gd incorporation, these NRs possess favorable electrical properties with a significant mobility of 177 cm2 (V.s)-1 compared to that reported in literature. Nonetheless significant challenges need to be overcome to achieve reproducible and stable p-type ZnO for commercial applications. Hence, several attempts based on n-type ZnO grown on foreign p-type substrates were made to achieve high-performance devices and overcome the issues arising when p-type doped ZnO is employed. Moreover, Growth of ZnO nanostructures on a foreign p-type substrates does not require a lattice-matched p-type substrate. Thus, for the first time, PLD conditions are improved to grow high quality ZnO nanotubes (NTs) with high optical, structural and electrical properties on a p-type Si (100) substrate without catalyst for high-performance devices. A fabrication of high performance UV photodetector (PD) based on ZnO NT/p-Si is demonstrated with superior responsivity (up to ~ 101.2 AW-1) compared to that reported in literature. This new and simple method demonstrates that the PLD system has a significant potential for improving the performance of materials used in a wide range of electronic and optoelectronic applications.
    Citation
    Flemban, T. H. (2017). High Quality Zinc Oxide Thin films and Nanostructures Prepared by Pulsed Laser Deposition for Photodetectors. KAUST Research Repository. https://doi.org/10.25781/KAUST-0U7P8
    DOI
    10.25781/KAUST-0U7P8
    ae974a485f413a2113503eed53cd6c53
    10.25781/KAUST-0U7P8
    Scopus Count
    Collections
    PhD Dissertations; Physical Science and Engineering (PSE) Division; Material Science and Engineering Program

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