% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@PHDTHESIS{Cai:828405,
      author       = {Cai, Biya},
      title        = {{M}anipulating the {S}tructural and
                      {E}lectronic{P}roperties of {E}pitaxial {N}a{N}b{O}$_{3}$
                      {F}ilms via {S}trainand {S}toichiometry},
      volume       = {136},
      school       = {Universität Köln},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2017-02366},
      isbn         = {978-3-95806-185-9},
      series       = {Schriften des Forschungszentrums Jülich. Reihe
                      Schlüsseltechnologien / Key Technologies},
      pages        = {VI, 114 S.},
      year         = {2016},
      note         = {Universität Köln, Diss., 2016},
      abstract     = {Due to their intriguing dielectric, pyroelectric,
                      elasto-electric, or opto-electric properties, oxide
                      ferroelectrics are vital candidates for the fabrication of
                      most electronics. However, these extraordinary properties
                      exist mainly in the temperature regime around the
                      ferroelectric phase transition, which is usually several
                      hundreds of K away from room temperature. Therefore, the
                      manipulation of oxide ferroelectrics, especially moving the
                      ferroelectric transition towards room temperature, is of
                      great interest for application and also basic research. In
                      this thesis, we demonstrate this using examples of
                      NaNbO$_{3}$ films. We show that the transition temperature
                      of these films can be modified via plastic strain caused by
                      epitaxial film growth on a structurally mismatched
                      substrate, and this strain can be fixed by controlling the
                      stoichiometry. The structural and electronic properties of
                      Na$_{1+x}$NbO$_{3+δ}$ thin films are carefully examined
                      byamong others XRD (e.g. RSM) and TEM and cryoelectronic
                      measurements. Especially the electronic features are
                      carefully analyzed via specially developed interdigitated
                      electrodes in combination with integrated temperature sensor
                      and heater. The electronic data are interpreted using
                      existing as well as novel theories and models, they are
                      proved to be closely correlated to the structural
                      characteristics. The major results are:-
                      Na$_{1+x}$NbO$_{3+δ}$ thin films can be grown epitaxially
                      on (110)NdGaO$_{3}$ with a thickness up to 140nm (thicker
                      films have not been studied). Plastic relaxation of the
                      compressive strain sets in when the thickness of the film
                      exceeds approximately 10 – 15 nm. Films with excess Na are
                      mainly composed of NaNbO$_{3}$ with minor contribution of
                      Na$_{3}$NbO$_{4}$. The latter phase seems to form
                      nanoprecipitates that are homogeneously distributed in the
                      NaNbO$_{3}$ film which helps to stabilize the film and
                      reduce the relaxation of the strain. - For the nominally
                      stoichiometric films, the compressive strain leads to a
                      broad and frequency-dispersive phase transition at lower
                      temperature (125 – 147 K). This could be either a new
                      transition or a shift in temperature of a known transition.
                      Considering the broadness and frequency dispersion of the
                      transition, this is actually a transition from the
                      dielectric state at high temperature to a relaxor-type
                      ferroelectric state at low temperature. The latter is based
                      on the formation of polar nano-regions (PNRs). Using the
                      electric field dependence of the freezing temperature,
                      allows a direct estimation of the volume (70 to270 nm$^{3}$)
                      and diameter (5.2 to 8 nm, spherical approximation) of the
                      PNRs. The values confirm with literature values which were
                      measured by other technologies. [...]},
      cin          = {PGI-8 / ICS-8},
      cid          = {I:(DE-Juel1)PGI-8-20110106 / I:(DE-Juel1)ICS-8-20110106},
      pnm          = {899 - ohne Topic (POF3-899)},
      pid          = {G:(DE-HGF)POF3-899},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:0001-2017032812},
      url          = {https://juser.fz-juelich.de/record/828405},
}