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@PHDTHESIS{BANG:641899,
      author       = {BANG, JOOHEE},
      othercontributors = {Thomas, Weber and Fiebig, Manfred},
      title        = {{N}on-invasive three-dimensional probing of atomic order in
                      single-crystalline thin films},
      school       = {ETH Zurich},
      type         = {Dissertation},
      address      = {Zurich},
      publisher    = {ETH Zurich},
      reportid     = {PUBDB-2025-05245},
      pages        = {108},
      year         = {2025},
      note         = {Dissertation, ETH Zurich, 2025},
      abstract     = {The emergence of powerful synchrotron sources, fast pixel
                      detectors, and the increasingavailability of
                      high-performance computing has facilitated the acquisition
                      and analysisof high-quality, large-volume diffuse
                      scattering data, providing insights into the realstructures
                      of disordered crystals that were not previously possible.
                      However, its ap-plication to studying local structural order
                      in thin films remains largely unexplored.This limitation
                      arises from the strong substrate contributions, which
                      obscures the weakdiffuse scattering signals from the film,
                      as well as the restricted reciprocal space cov-erage and
                      resolution inherent in grazing incidence X-ray diffraction.
                      This doctoralwork pioneers the extension of single-crystal
                      diffuse X-ray scattering techniques tothin films, enabling
                      atomic-scale characterization of complex domain structures
                      andtheir correlations within and across layers.We introduce
                      and validate a novel methodology for the structural
                      characteriza-tion of single-crystalline thin films,
                      overcoming challenges associated with non-invasiveprobing of
                      nanoscale domain configurations. A key accomplishment is the
                      implemen-tation of high-energy ultra-small grazing-incidence
                      X-ray diffraction, which effectivelymitigates substrate
                      contributions while achieving large reciprocal space
                      coverage andhigh sensitivity to small atomic displacements.
                      The large-volume and high-resolutiondiffuse scattering data
                      is analyzed using three-dimensional difference pair
                      distributionfunction (3D-ΔPDF), which provides invaluable
                      insights into the local atomic structureof
                      single-crystalline thin films.The methodology is first
                      applied to disordered oxide perovskite thin films, wherewe
                      establish a framework for interpreting 3D-ΔPDF features
                      associated with oxygenoctahedral tilts and cation
                      displacements. The approach is successfully validated onthe
                      known structure of SrRuO3 on SrTiO3, revealing a+a−c−
                      tilts and picometer-scalecation shifts with superior spatial
                      resolution compared to other characterization meth-ods.
                      Furthermore, correlation lengths and rotational amplitudes
                      of the oxygen octahe-dral tilts are analyzed as a function
                      of layer thickness and temperature, demonstratingthe
                      potential of the methodology in quantitative analysis.
                      Central to the analysis isthe divide-and-conquer approach
                      that allows for the selective examination of
                      diffusescattering features and ΔPDF signals with distinct
                      structural properties, showcasingthe versatility of the
                      methodology.ivBuilding on this validated framework, we
                      extend our approach to studying com-plex polarization domain
                      correlations in ferroelectric PbTiO3 and dielectric
                      SrTiO3(PTO|STO) superlattices. Our findings reveal the
                      presence of domain correlationswithin and across PTO layers,
                      extending into adjacent STO layers. We also investi-gated
                      temperature-dependent phase transitions of the domain
                      correlations and iden-tified two low-temperature phases with
                      strong anisotropic diffuse scattering and
                      onehigh-temperature pattern with ring-like appearance. In
                      general, thermal stability ofthe low-temperature
                      configurations increases in superlattices with higher
                      bilayer thick-ness, and the isotropic configuration emerges
                      at temperatures significantly above roomtemperature. On the
                      other hand, the only examined superlattice structure,
                      wherethe PTO layers are thicker than the STO layers,
                      exhibits ring-like scattering even atroom-temperature,
                      suggesting that thicker PTO layers experience reduced
                      anisotropicstrain from the STO layers.Finally, complementary
                      3D-ΔPDF analysis reveals the presence of Néel-type do-main
                      walls in the investigated superlattices. A major
                      breakthrough of this work isthe non-invasive probing of
                      buried layers within the superlattices, which unveils
                      aquadratic-shaped flux-closure polarization configuration
                      induced by tetragonal straineffects — an observation
                      rarely achieved with conventional characterization
                      methods.This demonstrates the method’s capability to
                      identify local structural chirality, a keyfeature in many
                      complex materials hosting nontrivial topologies.},
      keywords     = {info:eu-repo/classification/ddc/530 (Other) /
                      info:eu-repo/classification/ddc/500 (Other) / Physics
                      (Other) / Natural sciences (Other)},
      cin          = {FS DOOR-User},
      cid          = {$I:(DE-H253)FS_DOOR-User-20241023$},
      pnm          = {6G3 - PETRA III (DESY) (POF4-6G3)},
      pid          = {G:(DE-HGF)POF4-6G3},
      experiment   = {EXP:(DE-H253)P-P07-20150101},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.3929/ETHZ-B-000738059},
      url          = {https://bib-pubdb1.desy.de/record/641899},
}