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@INPROCEEDINGS{Winkler:827193,
      author       = {Winkler, Florian and Tavabi, Amir H. and Barthel, Juri and
                      Duchamp, Martial and Yucelen, Emrah and Borghardt, Sven and
                      Kardynal, Beata and Dunin-Borkowski, Rafal},
      title        = {{Q}uantitative measurement of mean inner potential and
                      specimen thickness from high-resolution off-axis electron
                      holograms of ultra-thin layered {WS}e2},
      address      = {Weinheim, Germany},
      publisher    = {Wiley-VCH Verlag GmbH $\&$ Co. KGaA},
      reportid     = {FZJ-2017-01391},
      pages        = {417 - 418},
      year         = {2016},
      comment      = {European Microscopy Congress 2016: Proceedings},
      booktitle     = {European Microscopy Congress 2016:
                       Proceedings},
      abstract     = {Off-axis electron holography is a powerful tool to measure
                      electrostatic and magnetic fields at the nanoscale inside a
                      transmission electron microscope. The electron wave that has
                      passed through a thin specimen can be recovered from an
                      electron hologram and the phase can be related to the
                      specimen thickness or the electrostatic potential in and
                      around the specimen. However, dynamical diffraction may
                      cause a deviation from the expected linear relationship
                      between phase and specimen thickness, which emphasizes the
                      need for comparisons with corresponding computer
                      simulations.Here, we study few-layer-thick two-dimensional
                      WSe2 flakes by off-axis electron holography. Voronoi
                      tessellation is used to spatially average the phase and
                      amplitude of the electron wavefunction within regions of
                      unit-cell size (see Fig. 1). A determination of specimen
                      thickness of the WSe2 is not possible from either the phase
                      or the amplitude alone. Instead, we show that the combined
                      analysis of phase and amplitude from experimental
                      measurements and simulations allows an accurate
                      determination of the local specimen thickness. Extremely
                      thin specimens that are tilted slightly away from the [001]
                      zone axis show an approximately linear relationship between
                      phase and projected potential. If the specimen thickness is
                      known, the electrostatic potential can be determined from
                      the measured phase.We used this combined approach to
                      determine a value for the mean inner potential of 18.9 ±
                      0.8 V for WSe2, which is approximately $10\%$ lower than the
                      value calculated from neutral atom scattering factors. In
                      this way, a comparison of high-resolution electron
                      holography data with simulations has been achieved on a
                      quantitative level, enabling an assessment of the
                      experimental conditions under which electrostatic potentials
                      can be extracted directly from the phases of measured
                      wavefunctions.The authors are grateful to L. Houben, M.
                      Lentzen, A. Thust, J. Caron and C. B. Boothroyd for
                      discussions, as well as A. Chaturvedi and C. Kloc from the
                      School of Materials Science and Engineering, Nanyang
                      Technological University, Singapore for providing the WSe2
                      crystals. We are also grateful to the European Research
                      Council for an Advanced Grant and for funding by the German
                      Science Foundation (DFG) grant MA 1280/40-1},
      month         = {Aug},
      date          = {2016-08-28},
      organization  = {16th European Microscopy Congress (EMC
                       2016), Lyon (France), 28 Aug 2016 - 2
                       Sep 2016},
      cin          = {PGI-5 / ER-C-1 / PGI-9},
      cid          = {I:(DE-Juel1)PGI-5-20110106 / I:(DE-Juel1)ER-C-1-20170209 /
                      I:(DE-Juel1)PGI-9-20110106},
      pnm          = {143 - Controlling Configuration-Based Phenomena (POF3-143)},
      pid          = {G:(DE-HGF)POF3-143},
      typ          = {PUB:(DE-HGF)8 / PUB:(DE-HGF)7},
      doi          = {10.1002/9783527808465.EMC2016.6494},
      url          = {https://juser.fz-juelich.de/record/827193},
}