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@INPROCEEDINGS{Ritz:827197,
      author       = {Ritz, Robert and Huth, Martin and Ihle, Sebastian and
                      Simson, Martin and Soltau, Heike and Migunov, Vadim and
                      Duchamp, Martial and Dunin-Borkowski, Rafal and Ryll,
                      Henning and Strüder, Lothar},
      title        = {{I}maging of {E}lectric {F}ields with the pn{CCD}
                      ({S}){TEM} {C}amera},
      address      = {Weinheim, Germany},
      publisher    = {Wiley-VCH Verlag GmbH $\&$ Co. KGaA},
      reportid     = {FZJ-2017-01395},
      pages        = {376 - 377},
      year         = {2016},
      comment      = {European Microscopy Congress 2016: Proceedings},
      booktitle     = {European Microscopy Congress 2016:
                       Proceedings},
      abstract     = {The imaging of electric fields on the nanometer scale is of
                      great interest for modern materials research. Techniques
                      providing a fast, direct and precise measurement of local
                      fields are thus useful for materials science applications.
                      We present microscopic measurements of electric fields with
                      the 4D-STEM technique using the pnCCD (S)TEM camera. In
                      4D-STEM, a 2D camera image is recorded for each probe
                      position of a 2D scan area, yielding a 4D dataset. With this
                      technique, small shifts of the bright field disc (BFD) due
                      to a deflection of the electron beam through electric and
                      magnetic fields in the sample region can be detected. Hence,
                      the magnitude and direction of the local field at each probe
                      position can be determined. Given the large number of
                      necessary probe positions, this technique requires a fast
                      camera system providing short enough readout times so that
                      instabilities in the microscope and sample drift or
                      radiation damage do not deteriorate the final STEM image.
                      Furthermore, a pixelated detector is required to record and
                      account for the intensity distribution variations caused by
                      interaction of the electron beam with the sample.The pnCCD
                      (S)TEM camera allows fast acquisition of 2D camera images
                      with a direct detecting, radiation hard pnCCD with 264×264
                      pixels [1]. Routinely, the readout speed is 1000 frames per
                      second (fps) and can be further increased through binning
                      and windowing. For example, with the pnCCD (S)TEM camera a
                      256x256 STEM image – where a camera image is recorded at
                      each probe position – can be recorded in less than 70 s.
                      The 264x264 pixel camera image allows precise determination
                      of the BFD position, yielding information about electric and
                      magnetic fields in the sample. For data analysis, image
                      subsets can be selected freely to obtain virtual diffraction
                      images or perform differential phase contrast (DPC)
                      analysis. A major advantage over conventional segmented DPC
                      detectors is that, with the pnCCD (S)TEM camera, movements
                      of the BFD can be discriminated from intensity variations
                      inside the BFD which is of particular importance for
                      analysis of electromagnetic fields inside specimens. Further
                      4D-STEM applications benefitting from the pnCCD (S)TEM
                      camera include imaging on the micro- and millisecond
                      timescale [2], strain analysis [3], magnetic domain mapping
                      [1], and electron ptychography [4].A demonstration of
                      electric field mapping in vacuum with the pnCCD (S)TEM
                      camera is shown in Figure 1. A voltage of 50 V was applied
                      to a tungsten needle mounted in an FEI Titan G2 80-200
                      ChemiSTEM microscope, operated at 80 keV. For each of the
                      256x256 probe positions, a 2D camera image was recorded
                      (Fig. 1a). From these camera images an incoherent bright
                      field STEM image (Fig. 1b, background) as well as the
                      position in the x- and y-directions of the BFD at each probe
                      position was calculated. A comparison of the position of the
                      BFD with and without an applied voltage yields information
                      about the magnitude and direction of the local gradient of
                      the projected electrostatic potential (Fig. 1b, indicated by
                      coloring and arrows). In addition to this direct mapping of
                      the electric field around a needle with rather well-shaped
                      BFDs, the large number of pixels of the pnCCD (S)TEM camera
                      allows the precise determination of the BFD position, even
                      in cases when the BFD is weak and deformed through the
                      interaction of the electron beam with the sample (Fig.
                      1c).In conclusion, 4D-STEM techniques like electromagnetic
                      field mapping benefit significantly from the capabilities of
                      the pnCCD (S)TEM camera. The readout speeds of 1000 fps and
                      above allow the fast acquisition of 4D datasets with 2D
                      camera images at each probe position. Through the large
                      number of pixels, position and intensity variations of BFDs
                      can be precisely determined.},
      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.EMC2016.6328},
      url          = {https://juser.fz-juelich.de/record/827197},
}