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@PHDTHESIS{CorleyWiciak:1023393,
author = {Corley-Wiciak, Agnieszka Anna},
othercontributors = {Grützmacher, Detlev and Mayer, Joachim and Capellini,
Giovanni},
title = {{C}haracterisation and optimisation of
${S}i_{y}{G}e_{1-x-y}{S}n_{x}$ alloys towards integrated
thermoelectric devices},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {RWTH Aachen University},
reportid = {RWTH-2025-10652},
pages = {1 Online-Ressource : Illustrationen},
year = {2025},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University 2026; Dissertation, RWTH Aachen University, 2025},
abstract = {Nowadays, a major challenge towards improving the
performance of microchips and processors is the management
of power consumption and heat dissipation within dense
arrays of devices. This issue could potentially be addressed
by the development of integrated thermoelectric generators
(TEGs), which convert on-chip waste heat into electricity.
However, most common thermoelectric materials used today are
incompatible with Complementary Metal-Oxide-Semiconductor
(CMOS) processing. An alternative material platform for
CMOS-integrated active on-chip coolers are alloys composed
of carbon (C), tin (Sn), and silicon (Si) combined with
germanium (Ge). Due to their direct bandgap and high carrier
mobility, the electronic and optical properties of these
group IV alloys have been the object of intensive research.
Meanwhile, their thermal properties have received
comparatively little attention. The significant alloy
scattering due to mass fluctuations in (C:)(Si)Ge1-x-ySnx
alloys affects phonon transport and may play a crucial role
in shaping their thermoelectric performance. This thesis
helps to close this knowledge gap by investigation of the
thermal characteristics of (C:)(Si)Ge1-xSnx alloys,
focussing on several factors that impact their
thermoelectric efficiency. The major objective is to gain
deeper insight into the mechanisms that lead to reduction in
lattice thermal conductivity within C:(Si)Ge1-xSnx, thus
contributing to a fundamental understanding of the dynamics
of phonons in complex semiconductor alloys. For this
purpose, a systematic study is carried out by varying the
composition, growth conditions, and dislocation density of
the samples. Firstly, an in-depth analysis of critical
factors such as short-range ordering and phonon interactions
in (C:)(Si)Ge1-xSnx is provided through
polarisation-dependent Raman spectroscopy. This method
allows to reveal a trend of repulsion between Sn-Sn and
Si-Sn atomic pairs hasbeen revealed. Secondly, to
investigate the multi-phonons interactions, the impact of
temperature on the Raman shift in Ge1-xSnx layers was
explored. This study did not reveal a significant effect of
the Sn content on the phononic interactions of the alloy.
Lastly, the thermal conductivity of the Ge1-xSnx lattice was
examined using Raman thermometry and the 3ω method. The
most effective strategy to minimise thermal conductivity is
identified as targeting an Sn content of approximately
$14at.\%$ or by enhancing the defect density in alloys with
lower Sn concentrations. Together, the results presented in
this thesis shed light on how stoichiometry, structural
disorder, and phonon behaviour are interconnected in group
IV semiconductor alloys. In addition to advancing the
fundamental understanding of (C:)(Si)Ge1-x-ySnx, they offer
a guidance for engineering materials with tailored
thermoelectric properties.},
cin = {134610 / 130000},
ddc = {530},
cid = {$I:(DE-82)134610_20140620$ / $I:(DE-82)130000_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2025-10652},
url = {https://publications.rwth-aachen.de/record/1023393},
}
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