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@PHDTHESIS{Lanius:723175,
author = {Lanius, Martin},
othercontributors = {Grützmacher, Detlev and Morgenstern, Markus},
title = {{T}opological insulating tellurides : how to tune doping,
topology, and dimensionality},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
reportid = {RWTH-2018-224023},
pages = {1 Online-Ressource (144 Seiten) : Illustrationen},
year = {2018},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, RWTH Aachen University, 2018},
abstract = {The promise of dissipationless transport, protected by time
reversal symmetry, made the class of topological Insulators
(TIs) a hot topic in condensed matter physics. The current
carrying surface states are spin-polarized with linear
energy dispersion, while the bulk stays insulating. This
combination gives the opportunity to construct highly
conducting devices with low energy consumption or
applications in spintronics. Beside this, the combination
with superconductors (SC) opens new roads towards detecting
Majorana quasiparticles, which are predicted to occur at the
interface between a TI and a SC. Recent studies show that
especially the compounds consisting of Bi/Sb and Te are
strong 3D topological insulators. Experiments reveal an
unintentional background doping of these materials. In this
thesis methods to customize the properties and doping of TIs
are presented. The materials were hereby grown on Si(111) by
molecular beam epitaxy (MBE). Scanning probe microscopy
(STM/AFM), X-ray diffraction (XRD), scanning transmission
electron microscopy (STEM), and atom probe tomography (APT)
were used to characterize the surface and bulk properties of
the TI films. Angle-resolved photoemission spectroscopy
(ARPES) measurements were carried out under ultra-high
vacuum (UHV) conditions to determine the electronic
structure of the grown samples. First the p-type strong TI
$Sb_2$ $Te_3$ was investigated to determine the growth mode
depending on the film thickness. The surface
characterization reveals a high density of screw
dislocations and defects. The results were linked to the
topography of ternary $(Bi_x$ $〖Sb_(1-x))〗_2$ $Te_3$
compounds with a high Sb content. In the second experimental
chapter the growth of $Bi_1$ $Te_1$ was established.
Simulations showed that this material is a weak TI and also
a topological crystalline insulator (TCI). A ARPES study is
presented, evidencing the results of the simulation. From
XRD and STEM the crystalline structure of the natural
superlattice $〖(Bi_2)〗_1$ $〖(Bi_2$ $Te_3)〗_2$ is
precisely determined. The surface characterization shows a
smooth step flow growth with the formation of “super
steps”. A concept for customizing the electronical
properties of a TI is presented in the third experimental
chapter. By combining the p-type $Sb_2$ $Te_3$ with an
underlying n-type $Bi_2$ $Te_3$ film, a p-n heterostructure
was constructed. The surface morphology and crystalline
quality were studied by STM/AFM and XRD to determine the
influence of the virtual $Bi_2$ $Te_3$ substrate on the
overlying $Sb_2$ $Te_3$ film. ARPES and transport
measurements show the variability of the fermi level and the
carrier concentration. A detailed analysis by STEM/EDX and
APT reveals a diffusive interface and the formation of
several ternary compounds. Furthermore, the possibility to
grow a p-n heterostructure with $Bi_1$ $Te_1$ instead of
$Bi_2$ $Te_3$ is presented and investigated by AFM and XRD.
In the last chapter, the growth of $Bi_2$ $Te_3$ and $Sb_2$
$Te_3$ on pre-patterned substrates at a nanoscopic scale is
described. By using the selective growth of $Bi_2$ $Te_3$ on
different surfaces, it was established to grow ultrathin
$Bi_2$ $Te_3$ films on Si(111) nanostructures. The tendency
of the films to grow over the edges of the patterns built
the base for the realization of freestanding $Bi_2$ $Te_3$
films on special designed structures like pillar arrays.},
cin = {132310 / 130000},
ddc = {530},
cid = {$I:(DE-82)132310_20140620$ / $I:(DE-82)130000_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2018-224023},
url = {https://publications.rwth-aachen.de/record/723175},
}
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