The interplay of Dirac physics and induced superconductivity at the interface of a 3D topological insulator (TI) with an s-wave superconductor (S) provides a new platform for topologically protected quantum computation based on elusive Majorana modes. To employ such S–TI hybrid devices in future topological quantum computation architectures, a process is required that allows for device fabrication under ultrahigh vacuum conditions. Here, we report on the selective area growth of (Bi,Sb)2Te3 TI thin films and stencil lithography of superconductive Nb for a full in situ fabrication of S–TI hybrid devices via molecular-beam epitaxy. A dielectric capping layer was deposited as a final step to protect the delicate surfaces of the S–TI hybrids at ambient conditions. Transport experiments in as-prepared Josephson junctions show highly transparent S–TI interfaces and a missing first Shapiro step, which indicates the presence of Majorana bound states. To move from single junctions towards complex circuitry for future topological quantum computation architectures, we monolithically integrated two aligned hardmasks to the substrate prior to growth. The presented process provides new possibilities to deliberately combine delicate quantum materials in situ at the nanoscale.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $15.58 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
König, M. et al. Quantum spin Hall insulator state in HgTe quantum wells. Science 318, 766–770 (2007).
Fu, L., Kane, C. L. & Mele, E. J. Topological insulators in three dimensions. Phys. Rev. Lett. 98, 106803 (2007).
Hsieh, D. et al. Observation of unconventional quantum spin textures in topological insulators. Science 323, 919–922 (2009).
Zhang, H. et al. Topological insulators in Bi2Se3, Bi2Te3 and Sb2Te3 with a single Dirac cone on the surface. Nat. Phys. 5, 438–442 (2009).
Fu, L. & Kane, C. L. Superconducting proximity effect and Majorana fermions at the surface of a topological insulator. Phys. Rev. Lett. 100, 096407 (2008).
Cook, A. & Franz, M. Majorana fermions in a topological-insulator nanowire proximity-coupled to an s-wave superconductor. Phys. Rev. B. 84, 201105 (2011).
Cook, A., Vazifeh, M. M. & Franz, M. Stability of Majorana fermions in proximity-coupled topological insulator nanowires. Phys. Rev. B 86, 155431 (2012).
Manousakis, J., Altland, A., Bagrets, D., Egger, R. & Ando, Y. Majorana qubits in a topological insulator nanoribbon architecture. Phys. Rev. B 95, 165424 (2017).
Kitaev, A. Y. Unpaired Majorana fermions in quantum wires. Phys. Usp. 44, 131–136 (2001).
Alicea, J. Majorana fermions in a tunable semiconductor device. Phys. Rev. B 81, 125318 (2010).
Kitaev, A. Y. Fault-tolerant quantum computation by anyons. Ann. Phys. 303, 2–30 (2003).
Aasen, D. et al. Milestones toward Majorana-based quantum computing. Phys. Rev. X 6, 031016 (2016).
Litinski, D., Kesselring, M. S., Eisert, J. & von Oppen, F. Combining topological hardware and topological software: color-code quantum computing with topological superconductor. Netw. Phys. Rev. X 7, 031048 (2017).
Alicea, J., Oreg, Y., Refael, G., Von Oppen, F. & Fisher, M. P. Non-Abelian statistics and topological quantum information processing in 1D wire networks. Nat. Phys. 7, 412–417 (2011).
Hyart, T. et al. Flux-controlled quantum computation with Majorana fermions. Phys. Rev. B 88, 035121 (2013).
van Heck, B., Akhmerov, A. R., Hassler, F., Burrello, M. & Beenakker, C. W. J. Coulomb-assisted braiding of Majorana fermions in a Josephson junction array. New J. Phys. 14, 035019 (2012).
Josephson, B. D. Possible new effects in superconductive tunnelling. Phys. Lett. 1, 251–253 (1962).
Golubov, A. A., Kupriyanov, M. Y. & Il’ichev, E. The current-phase relation in Josephson junctions. Rev. Mod. Phys. 76, 411–469 (2004).
Domínguez, F. et al. Josephson junction dynamics in the presence of 2π and 4π-periodic supercurrents. Phys. Rev. B 95, 195430 (2017).
Fu, L. Electron teleportation via Majorana bound states in a mesoscopic superconductor. Phys. Rev. Lett. 104, 056402 (2010).
Le Calvez, K. et al. Joule overheating poisons the fractional ac Josephson effect in topological Josephson junctions. Comm. Phys. 2, 4 (2019).
Bocquillon, E. et al. Gapless Andreev bound states in the quantum spin Hall insulator HgTe. Nat. Nanotechnol. 12, 137–143 (2017).
Wiedenmann, J. et al. 4π-periodic Josephson supercurrent in HgTe-based topological Josephson junctions. Nat. Com. 7, 10303 (2016).
Li, C. et al. 4π-periodic Andreev bound states in a Dirac semimetal. Nat. Mater. 17, 875–880 (2018).
Dominguez, F., Hassler, F. & Platero, G. Dynamical detection of Majorana fermions in current-biased nanowires. Phys. Rev. B 86, 140503 (2012).
Ngabonziza, P. et al. In situ spectroscopy of intrinsic Bi2Te3 topological insulator thin films and impact of extrinsic defects. Phys. Rev. B 92, 035405 (2015).
Thomas, C. R. et al. Surface oxidation of Bi2(Te,Se)3 topological insulators depends on cleavage accuracy. Chem. Mater. 28, 35–39 (2016).
Benia, H. M., Lin, C., Kern, K. & Ast, C. R. Reactive chemical doping of the Bi2Se3 topological insulator. Phys. Rev. Lett. 107, 177602 (2011).
Lang, M. R. et al. Revelation of topological surface states in Bi2Se3 thin films by in situ Al passivation. ACS Nano 6, 295–302 (2012).
Ngabonziza, P. et al. Gate-tunable transport properties of in situ capped Bi2Te3 topological insulator thin films. Adv. Electron Mater. 2, 1600157 (2016).
Schüffelgen, P. et al. Signatures of induced superconductivity in AlOx-capped topological heterostructures. Solid State Electron. 155, 111–116 (2019).
Kampmeier, J. et al. Selective area growth of Bi2Te3 and Sb2Te3 topological insulator thin films. J. Cryst. Growth 443, 38–42 (2016).
Christian, W. et al. Phase-coherent transport in selectively grown topological insulator nanodots. Nanotechnology 30, 055201 (2019).
Bohg, A. & Gaind, A. K. Influence of film stress and thermal oxidation on the generation of dislocations in silicon. Appl. Phys. Lett. 33, 895–897 (1978).
Moors, K. et al. Magnetotransport signatures of three-dimensional topological insulator nanostructures. Phys. Rev. B 97, 245429 (2018).
Ghatak, S. et al. Anomalous Fraunhofer patterns in gated Josephson junctions based on the bulk-insulating topological insulator BiSbTeSe2. Nano Lett. 18, 5124–5131 (2018).
van Woerkom, D. J., Geresdi, A. & Kouwenhoven, L. P. One minute parity lifetime of a NbTiN Cooper-pair transistor. Nat. Phys. 11, 547–550 (2015).
Schüffelgen, P. et al. Stencil lithography of superconducting contacts on MBE-grown topological insulator thin films. J. Cryst. Growth 477, 183–187 (2017).
Desplanque, L., Bucamp, A., Troadec, D., Patriarche, G. & Wallart, X. In-plane InSb nanowires grown by selective area molecular-beam epitaxy on semi-insulating substrate. Nanotechnology 29, 305705 (2018).
Aseev, P. et al. Selectivity map for molecular-beam epitaxy of advanced III–V quantum nanowire networks. Nano Lett. 19, 218–227 (2019).
Krizek, F. et al. Field effect enhancement in buffered quantum nanowire networks. Phys. Rev. Mat. 2, 093401 (2018).
Kampmeier, J. et al. Suppressing twin domains in molecular beam epitaxy grown Bi2Te3 topological insulator thin films. Cryst. Growth Des. 15, 390–394 (2016).
Kellner, J. et al. Tuning the Dirac point to the Fermi level in the ternary topological insulator (Bi1–xSbx)2Te3. Appl. Phys. Lett. 107, 251603 (2015).
Kovács, A., Schierholz, R. & Tillmann, K. FEI Titan G2 80-200 CREWLEY. J. Large-Scale Res. Facil. 2, A43 (2016).
A. Braginski and F. Hassler are acknowledged for enlightening discussions. M. Geitner and K.-H. Deussen are acknowledged for the deposition of Si3N4 and SiO2 layers. The authors thank G. Nagda and C. Beale for proofreading the manuscript. This work is supported by the German Science Foundation (DFG) under the priority program SPP1666 “Topological Insulators”, as well as by the Helmholtz Association via the “Virtual Institute for Topological Insulators” and the IVF project “Scalable Solid State Quantum Computing”.
The authors declare no competing interests.
Peer review information: Nature Nanotechnology thanks Torsten Karzig and other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Nature Nanotechnology (2019)