Gast ::
| Hauptseite > Publikationsdatenbank > Optimizing epitaxial growth of Bi2Te3 layers on sapphire towards high mobilities |
| Hauptseite > Publikationsdatenbank > Optimizing epitaxial growth of Bi2Te3 layers on sapphire towards high mobilities |
| Poster (After Call) | FZJ-2026-01427 |
; ; ;
2025
Abstract: Since the first proposal of creating Majorana bound states at the interface of a strong topological insulator and a superconductor [1], the interest in researching the properties of three-dimensional topological insulators has grown. Even though there were many different architectures for fault-tolerant Majorana-based quantum bits presented over the years [2-4], the two ingredients stayed the same, being a three dimensional topological insulator nanowire and a conventional s-wave superconductor. While there are several methods to prepare topological insulator thin films, molecular beam expitaxy promises to be the most scalable approach of creating pristine interfaces with the superconductor [5]. Therefore, in this work the method of epitaxially preparing topological insulators is employed. With various substrates available, we focused on sapphire substrates and worked on improving the growth of Bi2Te3, starting from optimizing the methods of chemical substrate cleaning, concluding in a sequence of Piranha solution and hydrofluoric acid etching. Further investigations were made to find an optimal Bi/Te atomic flux ratio in a Te-overpressure regime and a suitable substrate temperature, finally leading to twin-defect free crystals. We were aiming at high mobilities in cryogenic magnetotransport measurements in van der Pauw geometries, performed only hours after the crystal growth. All results are backed with X-ray diffraction analysis, showing correlations between crystal quality and electrical properties. Highest mobility samples show indications of significant surface transport of up to 40%, by Hall voltage non-linearities and by Shubnikov-de Haas oscillations revealing sheet carrier densities below 1⋅1012 cm-2. However, mobility values obtained by multi-channel Hall analysis and Dingle fits to quantum oscillations do differ by an order of magnitude, ranging from 2000 to 25000 cm2/Vs. This observation hints to a more complex explanation than classical multi-channel contributions from bulk and surface, like it was seen in cleaved bulk crystals in the past [6]. As the next step we plan to investigate the consistency of these anomalous effects and high mobilities from milli-/micrometer scale devices down to the nanometer regime, by ex-situ etching the material or using selective area epitaxy. This work was supported by JST within ASPIRE for rising scientists.[1] L. Fu, C. L. Kane, Phys. Rev. Lett. 100 096407 (2010).[2] S. Plugge et al., New J. Phys. 19 012001 (2017).[3] C. Schrade, L. Fu, Phys. Rev. Lett. 121, 267002 (2018).[4] R. Aguado, L. P. Kouwenhoven, Physics Today 73 (6), 44-50 (2020).[5] P. Schüffelgen, D. Rosenbach, C. Li, et al., Nat. Nanotechnol. 14, 825-831 (2019).[6] D.-X. Qu et al., Science 329, 821-824 (2010).
Keyword(s): Information and Communication (1st) ; Condensed Matter Physics (2nd)
|
The record appears in these collections: |
