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@ARTICLE{Tilgner:1047291,
      author       = {Tilgner, Niclas and Wolff, Susanne and Soubatch, Serguei
                      and Lee, Tien-Lin and Göhler, Fabian and Tautz, F Stefan
                      and Seyller, Thomas and Schädlich, Philip and Kumpf,
                      Christian},
      title        = {{S}olving the phase problem of diffraction: x-ray standing
                      wave imaging on bismuthene/{S}i{C}(0001)},
      journal      = {2D Materials},
      volume       = {12},
      number       = {4},
      issn         = {2053-1583},
      address      = {Bristol},
      publisher    = {IOP Publ.},
      reportid     = {FZJ-2025-04206},
      pages        = {045020},
      year         = {2025},
      abstract     = {For establishing a fundamental understanding of the
                      emerging properties of two-dimensional (2D) materials, a
                      reliable determination of the crystallographic structure is
                      essential, as we demonstrate in this work for the specific
                      case of the quantum spin Hall insulator bismuthene.
                      Diffraction-based methods are widely used for structure
                      determination, however, they suffer from a fundamental
                      shortcoming, the phase retrieval problem, that is the
                      inability to directly measure the phase of scattered waves.
                      The normal incidence x-ray standing wave (NIXSW) technique
                      circumvents this problem by introducing a Bragg-generated
                      x-ray standing wave field throughout the sample, relative to
                      which any atomic species can be localized. In essence, a
                      single NIXSW measurement captures the complex scattering
                      factor (amplitude and phase) corresponding to one single
                      Bragg reflection. Collecting data for multiple reflections
                      enables a three-dimensional reconstruction of the scattering
                      density as the Fourier sum of all measured scattering
                      factors. Here, we utilize this technique to reveal the
                      mechanism of a reversible switching process that has been
                      reported for a 2D Bi layer recently (Tilgner et al 2025 Nat.
                      Commun. 16, 6171). In this prominent example, the Bi layer
                      is confined between a 4H-SiC substrate and an epitaxial
                      graphene layer, and can be reversibly switched between an
                      electronically inactive precursor state and the bismuthene
                      state. In our NIXSW imaging experiment, we clearly identify
                      the change of the adsorption site of the Bi atoms, caused by
                      H-saturation of one out of three Si dangling bonds per unit
                      cell, as the key feature leading to the formation of the
                      characteristic band structure of the 2D bismuthene
                      honeycomb.},
      cin          = {PGI-3},
      ddc          = {530},
      cid          = {I:(DE-Juel1)PGI-3-20110106},
      pnm          = {5213 - Quantum Nanoscience (POF4-521) / DFG project
                      G:(GEPRIS)470743959 - Untersuchung der
                      Transporteigenschaften von interkaliertem Graphene auf
                      atomarer Skala (470743959) / SFB 1083 A12 - Struktur und
                      Anregungen von hetero-epitaktischen Schichtsystemen aus
                      schwach wechselwirkenden 2D-Materialien und molekularen
                      Schichten (A12) (385975694)},
      pid          = {G:(DE-HGF)POF4-5213 / G:(GEPRIS)470743959 /
                      G:(GEPRIS)385975694},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:001595688800001},
      doi          = {10.1088/2053-1583/ae0f27},
      url          = {https://juser.fz-juelich.de/record/1047291},
}