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@INPROCEEDINGS{Duchamp:827186,
      author       = {Duchamp, Martial and Girard, Olivier and Winkler, Florian
                      and Speen, Rolf and Dunin-Borkowski, Rafal},
      title        = {{F}abrication and characterization of a fine electron
                      biprism on a {S}i-on-insulator {MEMS} chip},
      address      = {Weinheim, Germany},
      publisher    = {Wiley-VCH Verlag GmbH $\&$ Co. KGaA},
      reportid     = {FZJ-2017-01384},
      pages        = {699 - 700},
      year         = {2016},
      comment      = {European Microscopy Congress 2016: Proceedings},
      booktitle     = {European Microscopy Congress 2016:
                       Proceedings},
      abstract     = {For off-axis electron holography, an electrostatic biprism
                      is usually located close to the selected area (SA) aperture
                      plane of the transmission electron microscope (TEM). The
                      application of a voltage to the biprism results in overlap
                      of two parts of an incident electron beam and allows both
                      the amplitude and phase of the electron wavefunction that
                      has passed through a specimen to be recovered. The quality
                      of the reconstructed electron wave depends directly on the
                      information contained in the hologram. An off-axis electron
                      hologram is characterized by its interference fringe
                      spacing, contrast and overlap width. The interference fringe
                      spacing and overlap width are determined by the electron
                      optics of the TEM and by the deflection angle at the
                      biprism. The interference fringe spacing is inversely
                      proportional to the deflection angle, while the overlap
                      width is influenced by the width of the biprism. In order to
                      achieve as narrow a fringe spacing as possible with high
                      fringe contrast, the biprism should be as narrow and stable
                      as possible. Previous attempts to make ultra-narrow biprisms
                      have included glass fibres coated with metal or patterned
                      SiNx with focused ion beam. None of these attempts have
                      provided a reproducible method of making ultra-narrow
                      biprisms with perfect control over their dimensions.Here, we
                      illustrate an approach that can be used to fabricate a
                      biprism that has a rectangular cross-section and is located
                      between two counter electrodes that are at the same height.
                      We pattern the biprism in the top Si layer of a
                      Si-on-insulator (SOI) wafer. The wafer consists of a
                      micron-thick single-crystalline Si layer that is isolated
                      electrically from its substrate and can be left
                      free-standing using an etching process. When combined with
                      microelectromechanical systems (MEMS) processes, structures
                      can be patterned down to nm scale in three dimensions. In
                      this way, the width of the biprism and the distance to the
                      counter-electrodes can be chosen to have dimensions down to
                      ˜100 nm. A further advantage of using an SOI wafer to
                      fabricate a biprism is the large Young's modulus of the
                      single-crystalline Si biprism (170 GPa), when compared with
                      that of a conventional biprism made from glass (˜70 GPa).
                      In addition, the two counter-electrodes can be biased
                      independently. A schematic diagram and scanning electron
                      microscopy (SEM) images of a biprism on an
                      electrically-contacted MEMS chip are shown in Fig. 1,
                      alongside a three-dimensional design drawing of a
                      custom-made aperture rod.In order to test its performance,
                      the biprism was mounted close to the SA plane in a Philips
                      CM20 TEM. The electron deflection was measured by recording
                      the shift of a diffraction spot as function of applied
                      voltage. The measured deflections are compared with
                      predicted deflections and with similar measurements made
                      using a conventional biprism on an FEI Titan TEM in Fig. 2.
                      The deflection is a factor two greater for the new
                      rectangular biprism for the same applied voltage. The
                      measured interference fringe spacing, contrast and overlap
                      width achieved using the new biprism are also shown in Fig.
                      2. Here, the maximum voltage that can be applied is limited
                      by the distance between the biprism and the
                      counter-electrodes, which can be increased in future
                      designs.In order to demonstrate the imaging capabilities of
                      the new biprism, an off-axis electron hologram of a MoS2
                      flake was recorded in a Philips CM20 TEM. The hologram and
                      the resulting reconstructed amplitude and phase are shown in
                      Fig. 3. In the future, the biprism will be mounted in an
                      image-aberration-corrected FEI Titan TEM, in which the
                      electron optics offers greater flexibility in both normal
                      and Lorentz imaging modes.The authors acknowledge financial
                      support from the European Union under the Seventh Framework
                      Programme under a contract for an Integrated Infrastructure
                      Initiative (Reference 312483 ESTEEM2), the European Research
                      Council for an Advanced Grant (Reference 320832 IMAGINE) and
                      for Starting Grant (Reference 306535 HOLOVIEW) for financial
                      support. We thank David Cooper and Helmut Soltner for
                      valuable discussions and support.},
      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},
      cid          = {I:(DE-Juel1)PGI-5-20110106 / I:(DE-Juel1)ER-C-1-20170209},
      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.EMC2016.6259},
      url          = {https://juser.fz-juelich.de/record/827186},
}