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@PHDTHESIS{Dzhigaev:318558,
      author       = {Dzhigaev, Dmitry},
      othercontributors = {Vartaniants, Ivan and Schroer, Christian},
      title        = {{C}haracterization of nanowires by coherent x-ray
                      diffractive imaging and ptychography},
      issn         = {1435-8085},
      school       = {Universität Hamburg},
      type         = {Dr.},
      address      = {Hamburg},
      publisher    = {Verlag Deutsches Elektronen-Synchrotron},
      reportid     = {PUBDB-2017-01266, DESY-THESIS-2017-008},
      series       = {DESY-THESIS},
      pages        = {149},
      year         = {2017},
      note         = {Universität Hamburg, Diss., 2017},
      abstract     = {Imaging techniques are of paramount importance for our
                      understanding of the universe. From galaxies and stars
                      explored by huge telescopes down to micro and nanostructures
                      studied by microscopes, imaging systems provide invaluable
                      scientific information. When an object under investigation
                      has a size of about 100 nanometers, x-rays become a perfect
                      probe for non-destructive imaging. The manufacturing process
                      of image forming lenses for x-rays becomes much more
                      complicated comparing to optical ones. Therefore,
                      ”lensless” techniques which rely on the coherent
                      properties of radiation were developed. With third
                      generation of synchrotron sources highly coherent and
                      intense x-ray beams became widely accessible. They are used
                      in new imaging methods such as coherent x-ray diffractive
                      imaging (CXDI) and x-ray ptychography. Modern nanotechnology
                      opens a wide spectrum of possible applications in different
                      branches of physics, chemistry, biology and engineering. At
                      the nanoscale, matter has different physical and chemical
                      properties compared to the macroscale bulk material.
                      Thecontinuing trend of miniaturization of functional
                      components in semiconductor industry brings new challenges
                      both in growth and characterization methods. This Thesis is
                      focusedon application of coherent diffractive imaging
                      methods to reveal the structure of single semiconductor
                      nanowires (NWs). They have been attracting significant
                      attention for a couple of decades due to their efficient
                      strain relaxation properties. And since the strain plays a
                      significant role in NW performance the projects carried out
                      in this work are oriented on Bragg CXDI approaches. Three
                      distinct projects were carried out during my research
                      activity at DESY research center of the Helmholtz
                      Association. Experimental work was performed at P06 and P10
                      beamlines at PETRA III synchrotron. The first part of this
                      Thesis extends the application of the three-dimensional (3D)
                      Bragg CXDI to strain field mapping in a single InP NW with a
                      diameter of 100 nm. The measurement employed a nanofocused
                      beam, which is characterized by transmission x-ray
                      ptychography. It is shown that the separation of the object
                      and probe functions is possible in the direct space after a
                      3D reconstruction. The influence of a catalyst particle at
                      the tip of the NW on the strain distribution in InP part of
                      the NW is revealed. The second part of the manuscript is
                      dedicated to the development and application of
                      two-dimensional x-ray Bragg ptychography (2D XBP) to studies
                      of single NWs. This approach providesa larger field of view
                      on the sample and the reliability of reconstruction results
                      improves, due to the advantages of ptychography. The
                      limitations of the technique are discussed bytheoretical
                      analysis and finite element method modeling (FEM).
                      Successful experimental implementation is demonstrated on a
                      single InGaN/GaN core-shell NW. The third part isdevoted to
                      3D Bragg CXDI of strain evolution in a single GaNNWwith
                      respect to applied voltage bias. A complicated tilting and
                      defect formation process in the NW was revealedfrom the
                      evolution of the Bragg peak. This study gives an insight
                      into piezoelectrical properties of the sample, which
                      dramatically influence electron-hole pair recombinationand
                      may decrease the efficiency of optoelectronic devices based
                      on GaN NWs.},
      cin          = {FS-PS},
      cid          = {I:(DE-H253)FS-PS-20131107},
      pnm          = {6214 - Nanoscience and Materials for Information Technology
                      (POF3-621) / 6G3 - PETRA III (POF3-622) / NWS4LIGHT -
                      Nanowires for solid state lighting (280773) / VH-VI-403 -
                      In-Situ Nano-Imaging of Biological and Chemical Processes
                      $(2015_IFV-VH-VI-403)$},
      pid          = {G:(DE-HGF)POF3-6214 / G:(DE-HGF)POF3-6G3 /
                      G:(EU-Grant)280773 / $G:(DE-HGF)2015_IFV-VH-VI-403$},
      experiment   = {EXP:(DE-H253)P-P06-20150101 / EXP:(DE-H253)P-P10-20150101},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)29 / PUB:(DE-HGF)11},
      doi          = {10.3204/PUBDB-2017-01266},
      url          = {https://bib-pubdb1.desy.de/record/318558},
}