Insights into the Screw-Dislocation Mediated Growth Mechanism in Double Shell Heterostructures of Bi 2Te 3-Sb 2Te 3-Bi 2Te 3: A STEM Study

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Insights into the Screw-Dislocation Mediated Growth Mechanism in Double Shell Heterostructures of Bi ₂Te ₃-Sb ₂Te ₃-Bi ₂Te ₃: A STEM Study

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Author(s): Naveen Goyal ¹ ^, , Koushik Jagadish ¹ , N. Ravishankar ¹ ^,

Publication date (Electronic): 21 January 2025

Conference name: 13th Asia Pacific Microscopy Congress 2025 (APMC13)

Conference date: 2-7 Febuary 2025

Keywords: 2D layered materials and heterostrutures, Atomic resolution STEM, Screw-dislocations, Defect propagation

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Abstract

Synthesizing nanocrystals particularly heterostructures, containing two or more elements/compounds using simple one pot synthetic method is always challenging since controlling epitaxial growth in heterostructures along with morphology, nucleation and growth time is a typical task [ 1]. Herein, we have developed first time a one-pot wet chemical synthetic method for core-shell heterostructure of Bi ₂Te ₃-Sb ₂Te ₃ (BT-ST) by adjusting the growth kinetics of individual BT and ST. Both these materials have quintuple layered structure and potential candidates of photodetection and thermoelectric materials [ 2]. HAADF-STEM micrograph of as-synthesized BT-ST heterostructure is depicted in Figure 1(a) along with EDS maps displaying core is made up of BT while shell contain ST. The epitaxial relationship of grown BT-ST is turned out to be (11 2 ¯ 0) Bi ₂Te ₃ // (11 2 ¯ 0) Sb ₂Te ₃. This in-plane lateral heterostructure of BT-ST is further employed for growth of another layer of BT by careful optimization of thermodynamic parameters, resulted in the growth of double-shell heterostructure of BT-ST-BT. HAADF-STEM micrograph and corresponding EDS maps in Figure 1(b) shows the formation of BT-ST-BT nanosheet with BT core and alternate shell of ST and BT.

Figure 1:

(a) HAADF-STEM micrograph and corresponding EDS map of Bi, Sb and Te depicting formation of core-shell Bi ₂Te ₃-Sb ₂Te ₃ nanostructure; (b) HAADF-STEM micrograph and EDS maps depicting formation of double shell Bi ₂Te ₃-Sb ₂Te ₃-Bi ₂Te ₃ heterostructure.

Both BT and ST are known to grow using screw-dislocation mediated growth mechanism, but exact atomic arrangement of this screw-dislocation is not known till yet [ 1]. Additionally, it is important to understand the defect propagation in heterostructures of BT-ST-BT. To elucidate the growth mechanism in case of heterostructures, we have employed cross-section STEM analysis. The cross-section sample was prepared using FIB-SEM to visualize the layer stacking sequence in the nanosheet. HAADF-STEM micrograph in Figure 2(a) shows the side view of the BT-ST-BT nanosheet, clearly depicting the presence of steps on the surface, providing evidence for the screw-dislocation growth mechanism.

Figure 2:

(a) HAADF-STEM micrograph showing steps on the surface of BT-ST heterostructure; (b) Atomic-resolution image providing evidence of screw dislocations present at the interface; (c) Schematic depicting the formation of 5-layer 7-layer structure due to presence of screw dislocations; (d) Magnified image of (b) showing propagation of screw dislocations along (0001).

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Author and article information

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Publication date (Electronic): 21 January 2025

Electronic Location Identifier: e360

Affiliations

[1 ]Materials Research Centre, Indian Institute of Science, Bangalore-560012, India

Author notes

*Corresponding authors: naveengoyal@ 123456iisc.ac.in , nravi@ 123456iisc.ac.in

Author information

Naveen Goyal https://orcid.org/0000-0002-8827-2646

Koushik Jagadish https://orcid.org/0000-0001-8856-5310

N. Ravishankar https://orcid.org/0000-0003-0012-046X

Article

DOI: 10.14293/APMC13-2025-0360

SO-VID: 6f7186bf-337c-4cb9-973b-dc574269eff6

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Published under Creative Commons Attribution 4.0 International ( CC BY 4.0). Users are allowed to share (copy and redistribute the material in any medium or format) and adapt (remix, transform, and build upon the material for any purpose, even commercially), as long as the authors and the publisher are explicitly identified and properly acknowledged as the original source.

Conference name: 13th Asia Pacific Microscopy Congress 2025

Conference acronym: APMC13

Conference number: 13

Conference location: Brisbane, Australia

Conference date: 2-7 Febuary 2025

History

Funding

Funded by: Advanced Facility of Microscopy and Microanalysis (AFMM) IISc

The authors acknowledge Advanced Facility of Microscopy and Microanalysis (AFMM) IISc for providing TEM facilities and funding from the SERB and PMRF.

References

N. Goyal, et al., J. Phys. Chem. C 2024, 128, 18, 7784–7794. https://doi.org/10.1021/acs.jpcc.4c01472.
N. Goyal and N. Ravishankar, Microscopy and Microanalysis 30 (Suppl 1), 2024, 1155-1156. https://doi.org/10.1093/mam/ozae044.575.

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[1] N. Goyal, et al., J. Phys. Chem. C 2024, 128, 18, 7784–7794. https://doi.org/10.1021/acs.jpcc.4c01472.

[2] N. Goyal and N. Ravishankar, Microscopy and Microanalysis 30 (Suppl 1), 2024, 1155-1156. https://doi.org/10.1093/mam/ozae044.575.