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@ARTICLE{Bashir:861052,
      author       = {Bashir, A. and Gallacher, K. and Millar, R. W. and Paul, D.
                      J. and Ballabio, A. and Frigerio, J. and Isella, G. and
                      Kriegner, D. and Ortolani, M. and Barthel, J. and MacLaren,
                      I.},
      title        = {{I}nterfacial sharpness and intermixing in a {G}e-{S}i{G}e
                      multiple quantum well structure},
      journal      = {Journal of applied physics},
      volume       = {123},
      number       = {3},
      issn         = {1089-7550},
      address      = {Melville, NY},
      publisher    = {American Inst. of Physics},
      reportid     = {FZJ-2019-01636},
      pages        = {035703 -},
      year         = {2018},
      abstract     = {A Ge-SiGe multiple quantum well structure created by low
                      energy plasma enhanced chemical vapour deposition, with
                      nominal well thickness of 5.4 nm separated by 3.6 nm
                      SiGe spacers, is analysed quantitatively using scanning
                      transmission electron microscopy. Both high angle annular
                      dark field imaging and electron energy loss spectroscopy
                      show that the interfaces are not completely sharp,
                      suggesting that there is some intermixing of Si and Ge at
                      each interface. Two methods are compared for the
                      quantification of the spectroscopy datasets: a
                      self-consistent approach that calculates binary
                      substitutional trends without requiring experimental or
                      computational k-factors from elsewhere and a standards-based
                      cross sectional calculation. Whilst the cross section
                      approach is shown to be ultimately more reliable, the
                      self-consistent approach provides surprisingly good results.
                      It is found that the Ge quantum wells are actually about
                      $95\%$ Ge and that the spacers, whilst apparently peaking at
                      about $35\%$ Si, contain significant interdiffused Ge at
                      each side. This result is shown to be not just an artefact
                      of electron beam spreading in the sample, but mostly arising
                      from a real chemical interdiffusion resulting from the
                      growth. Similar results are found by use of X-ray
                      diffraction from a similar area of the sample. Putting the
                      results together suggests a real interdiffusion with a
                      standard deviation of about 0.87 nm, or put another
                      way—a true width defined from $10\%–90\%$ of the
                      compositional gradient of about 2.9 nm. This suggests an
                      intrinsic limit on how sharp such interfaces can be grown by
                      this method and, whilst $95\%$ Ge quantum wells (QWs) still
                      behave well enough to have good properties, any attempt to
                      grow thinner QWs would require modifications to the growth
                      procedure to reduce this interdiffusion, in order to
                      maintain a composition of $≥95\%$ Ge},
      cin          = {ER-C-2},
      ddc          = {530},
      cid          = {I:(DE-Juel1)ER-C-2-20170209},
      pnm          = {143 - Controlling Configuration-Based Phenomena (POF3-143)},
      pid          = {G:(DE-HGF)POF3-143},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000423028400040},
      doi          = {10.1063/1.5001158},
      url          = {https://juser.fz-juelich.de/record/861052},
}