Title page for etd-0713115-100614


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URN etd-0713115-100614
Author Jing-Wei Zhou
Author's Email Address No Public.
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Department Physics
Year 2014
Semester 2
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title Structures and dielectrics of sputtered epitaxial TiO2/HfO2 superlattices
Date of Defense 2015-07-28
Page Count 70
Keyword
  • Dielectric Constant
  • XRD
  • TEM
  • HfO2
  • Superlattice
  • TiO2
  • Abstract RF magnetron sputtering has been used to deposit thin films of TiO2/HfO2 superlattices
    in alternating sequence on c-oriented sapphire substrates using titanium, or titanium
    dioxide, and Hafnium dioxide targets. The thin films thus obtained have higher
    dielectric constants and better insulation properties. The dielectric characteristics were
    studied on samples of different numbers of cycles and thickness ratios of the two oxides.
    Two series of samples, classified as series-A for [(TiO21nm/HfO21nm)10cycles and
    (TiO23nm/HfO21nm)10cycles], and as series-B for [(TiO21nm/HfO21nm)5cycles and
    (TiO23nm/HfO21nm)5cycles]. X-ray diffractometry (XRD) and transmission electron
    microscopy (TEM) have been conducted to examine the structural properties of the
    samples in relation to the dielectric properties, and lock-in amplifier used to measure
    the internal impedance of the samples from 0.1 Hz to 100kHz. Change of voltage as a
    function of frequency was used to calculate the values the frequency dependence of
    involved capacitance and inductance.
    TEM electron diffraction patterns showed that the HfO2 layers are of a few
    nanometer thick and grow epitaxially on the TiO2 thin film by assuming the same
    crystal structure of the underlying TiO2 layer. Traditional wisdom suggests that TiO2
    thin films grown on c-sapphire should at best be twinned, if epitaxial at all. However,
    in this work, the structure of the obtained TiO2 was found to be epitaxial and twin-free.
    This is interpreted as associated with the overall chemical bonding forces among the Ti,
    O, and Al atoms of the TiO2 (011)-plane on sapphire (0001)-plane. This led to an ideal
    epitaxy with orientation relations of (TiO2)(011)//Al2O3(0001), TiO2[010]// Al2O3
    [1120] and TiO2[001]// Al2O3 [1010].
    Advisory Committee
  • Li-Wei Tu - chair
  • Chih-hsiung Liao - co-chair
  • Den -Jun Jang - co-chair
  • Quark Chen - advisor
  • Files
  • etd-0713115-100614.pdf
  • Indicate in-campus at 1 year and off-campus access at 5 year.
    Date of Submission 2015-08-28

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