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Nano Research 2020, 13(2): 570-575 https://doi.org/10.1007/s12274-020-2657-4
Research Article | Issue | Published: 13 February 2020

ALD growth of ultra-thin Co layers on the topological insulator Sb2Te3

Show Author's Information Emanuele Longo1,2,  Roberto Mantovan1( ),  Raimondo Cecchini1,  Michael D. Overbeek3,  Massimo Longo1,  Giovanna Trevisi4,  Laura Lazzarini4,  Graziella Tallarida1,  Marco Fanciulli2,  Charles H. Winter3,  Claudia Wiemer1( )
CNR-IMM, Unit of Agrate Brianza, Via C. Olivetti 2, Agrate Brianza (MB) 20864, Italy
Università degli Studi di Milano-Bicocca, Dipartimento di Scienza dei Materiali, Via R. Cozzi 55, Milano 20125, Italy
Department of chemistry, Wayne State University, Detroit, Michigan 48202, USA
CNR-IMEM, Parco Area delle Scienze 37/A, Parma 43124, Italy
Keywords:
atomic layer deposition, metal organic chemical vapor deposition, X-ray diffraction, spintronics, Co-fcc, Co-hcp, antimony telluride
Topics:
Antimony compoundsCobaltCrystal structureCrystallitesMetallorganic chemical vapor depositionNanocrystalline materials Organic chemicalsOrganometallicsSpintronics SubstratesSurface roughnessTellurium compoundsX-ray diffraction
Cite this article:
Longo E, Mantovan R, Cecchini R, et al. ALD growth of ultra-thin Co layers on the topological insulator Sb2Te3. Nano Research, 2020, 13(2): 570-575. https://doi.org/10.1007/s12274-020-2657-4
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Abstract Full text Electronic supplementary material About this article

Taking the full advantage of the conformal growth characterizing atomic layer deposition (ALD), the possibility to grow Co thin films, with thickness from several tens down to few nanometers on top of a granular topological insulator (TI) Sb2Te3 film, exhibiting a quite high surface roughness (2-5 nm), was demonstrated. To study the Co growth on the Sb2Te3 substrate, we performed simultaneous Co depositions also on sputtered Pt substrates for comparison. We conducted a thorough chemical-structural characterization of the Co/Sb2Te3 and Co/Pt heterostructures, confirming for both cases, not only an excellent conformality, but also the structural continuity of the Co layers. X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM) analyses evidenced that Co on Sb2Te3 grows preferentially oriented along the [00ℓ] direction, following the underlying rhombohedric substrate. Differently, Co crystallizes in a cubic phase oriented along the [111] direction when deposited on Pt. This work shows that, in case of deposition of crystalline materials, the ALD surface selectivity and conformality can be extended to the definition of local epitaxy, where in-plane ordering of the crystal structure and mosaicity of the developed crystallized grains are dictated by the underlying substrate. Moreover, a highly sharp and chemically-pure Co/Sb2Te3 interface was evidenced, which is promising for the application of this growth process for spintronics.


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Electronic supplementary material
About this article

ALD growth of ultra-thin Co layers on the topological insulator Sb2Te3

Show Author's information Emanuele Longo1,2, Roberto Mantovan1( ), Raimondo Cecchini1, Michael D. Overbeek3, Massimo Longo1, Giovanna Trevisi4, Laura Lazzarini4, Graziella Tallarida1, Marco Fanciulli2, Charles H. Winter3, Claudia Wiemer1( )
CNR-IMM, Unit of Agrate Brianza, Via C. Olivetti 2, Agrate Brianza (MB) 20864, Italy
Università degli Studi di Milano-Bicocca, Dipartimento di Scienza dei Materiali, Via R. Cozzi 55, Milano 20125, Italy
Department of chemistry, Wayne State University, Detroit, Michigan 48202, USA
CNR-IMEM, Parco Area delle Scienze 37/A, Parma 43124, Italy

Abstract

Taking the full advantage of the conformal growth characterizing atomic layer deposition (ALD), the possibility to grow Co thin films, with thickness from several tens down to few nanometers on top of a granular topological insulator (TI) Sb2Te3 film, exhibiting a quite high surface roughness (2-5 nm), was demonstrated. To study the Co growth on the Sb2Te3 substrate, we performed simultaneous Co depositions also on sputtered Pt substrates for comparison. We conducted a thorough chemical-structural characterization of the Co/Sb2Te3 and Co/Pt heterostructures, confirming for both cases, not only an excellent conformality, but also the structural continuity of the Co layers. X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM) analyses evidenced that Co on Sb2Te3 grows preferentially oriented along the [00ℓ] direction, following the underlying rhombohedric substrate. Differently, Co crystallizes in a cubic phase oriented along the [111] direction when deposited on Pt. This work shows that, in case of deposition of crystalline materials, the ALD surface selectivity and conformality can be extended to the definition of local epitaxy, where in-plane ordering of the crystal structure and mosaicity of the developed crystallized grains are dictated by the underlying substrate. Moreover, a highly sharp and chemically-pure Co/Sb2Te3 interface was evidenced, which is promising for the application of this growth process for spintronics.

Keywords: atomic layer deposition, metal organic chemical vapor deposition, X-ray diffraction, spintronics, Co-fcc, Co-hcp, antimony telluride

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Publication history
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Acknowledgements

Publication history

Received: 09 October 2019
Revised: 02 January 2020
Accepted: 13 January 2020
Published: 13 February 2020
Issue date: February 2020

Copyright

© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020

Acknowledgements

We acknowledge the MP1402-Hooking together the European research in atomic layer deposition (HERALD) COST action and the Horizon 2020 project SKYTOP "Skyrmion-Topological Insulator and Weyl Semimetal Technology" (FETPROACT-2018-01, n. 824123). Efforts at Wayne State University were supported by the U.S. National Science Foundation (Grant No. CHE-1607973) and EMD Performance Materials.

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