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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},
}