000851098 001__ 851098
000851098 005__ 20210129234731.0
000851098 037__ $$aFZJ-2018-04800
000851098 041__ $$aEnglish
000851098 1001_ $$0P:(DE-Juel1)165984$$aSchüffelgen, Peter$$b0$$eCorresponding author
000851098 245__ $$aExploiting Topological Insulators for Majorana Devices and Physics via Molecular Beam Epitaxy$$f - 2018-05-14
000851098 260__ $$c2018
000851098 300__ $$a146
000851098 3367_ $$2DataCite$$aOutput Types/Dissertation
000851098 3367_ $$2ORCID$$aDISSERTATION
000851098 3367_ $$2BibTeX$$aPHDTHESIS
000851098 3367_ $$02$$2EndNote$$aThesis
000851098 3367_ $$0PUB:(DE-HGF)11$$2PUB:(DE-HGF)$$aDissertation / PhD Thesis$$bphd$$mphd$$s1534322003_7415
000851098 3367_ $$2DRIVER$$adoctoralThesis
000851098 502__ $$aDissertation, RWTH Aachen University, 2018$$bDissertation$$cRWTH Aachen University$$d2018
000851098 520__ $$aThe prospect of fault-tolerant topological quantum computation (TQC) based on Majorana zero modes (MZM) motivated the fabrication of high quality hybrid structures comprised of three-dimensional (3D) topological insulators (TI) and s-wave superconductors (S). The work presented here, deals with the successive optimization of material growth and fabrication processes to pave the way towards scalable construction of hybrid devices for quantum computing applications. In order to protect the physical surfaces of Bi2-xSbxTe3 TIs grown via molecular beam epitaxy (MBE) from oxidation, thin films have to be capped in-situ, which makes device fabrication challenging. The simplest device to test whether or not a given combination of S and TI hosts desired Majorana excitations is a Josephson junction (JJ). JJs of first and second generation had a thin AlOx layer as capping. Ex-situ fabricated Nb electrodes showed a low transparency and only small dissipationless Josephson supercurrents could be induced. However, an attenuated first Shapiro step in transport experiments indicated signatures of possible Majorana contributions to the critical current. In order to reproduce and enhance these observations, novel fabrication techniques were established. Full fabrication of JJs under ultra-high vacuum (UHV) conditions via various stencil lithography techniques were pursuit in order to generate pristine S–TI interfaces. In addition, different superconductive materials (Al, Ti, Nb) were examined with regards to their suitability for in-situ defined electrodes. Fully in-situ fabricated junctions with Nb electrodes and stoichiometric Al2O3 capping showed a high interface transparency, large critical supercurrents and a fully suppressed first Shapiro step, indicating transport mediated by so-called Majorana bound states (MBS). Transmission electron microscopy (TEM) analysis confirmed a high S-TI interface quality and a fully capped weak link. These findings suggest that Nb as superconductive material in combination with the established stencil techniques is key towards hybrid devices based on Bi2-xSbxTe3 TIs. The fusion of stencil technique with selective area growth (SAG) allowed to combine networks of selectively grown topological nanostructures with superconductive electrodes of arbitrary geometry. This paves the way for flexible in-situ fabrication of scalable S-TI hybrid devices towards TQC applications.
000851098 536__ $$0G:(DE-HGF)POF3-524$$a524 - Controlling Collective States (POF3-524)$$cPOF3-524$$fPOF III$$x0
000851098 909CO $$ooai:juser.fz-juelich.de:851098$$pVDB
000851098 9101_ $$0I:(DE-588b)5008462-8$$6P:(DE-Juel1)165984$$aForschungszentrum Jülich$$b0$$kFZJ
000851098 9131_ $$0G:(DE-HGF)POF3-524$$1G:(DE-HGF)POF3-520$$2G:(DE-HGF)POF3-500$$3G:(DE-HGF)POF3$$4G:(DE-HGF)POF$$aDE-HGF$$bKey Technologies$$lFuture Information Technology - Fundamentals, Novel Concepts and Energy Efficiency (FIT)$$vControlling Collective States$$x0
000851098 9141_ $$y2018
000851098 920__ $$lyes
000851098 9201_ $$0I:(DE-Juel1)PGI-9-20110106$$kPGI-9$$lHalbleiter-Nanoelektronik$$x0
000851098 980__ $$aphd
000851098 980__ $$aVDB
000851098 980__ $$aI:(DE-Juel1)PGI-9-20110106
000851098 980__ $$aUNRESTRICTED