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Freestanding Nanolayers of a Wide‐Gap Topological Insulator through Liquid‐Phase Exfoliation
Author(s) -
Lê Anh Mai,
Potapov Pavel,
Wolf Daniel,
Lubk Axel,
Glatz Bernhard,
Fery Andreas,
Doert Thomas,
Ruck Michael
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202004320
Subject(s) - topological insulator , materials science , topology (electrical circuits) , exfoliation joint , condensed matter physics , graphene , nanotechnology , physics , mathematics , combinatorics
The layered salt Bi 14 Rh 3 I 9 is a weak three‐dimensional (3D) topological insulator (TI), that is, a stack of two‐dimensional (2D) TIs. It has a wide non‐trivial band gap of 210 meV, which is generated by strong spin‐orbit coupling, and possesses protected electronic edge‐states. In the structure, charged layers of∞2 [ (Bi 4 Rh) 3 I] 2+ honeycombs and∞1 [ Bi 2 I 8 ] 2− chains alternate. The non‐trivial topology of Bi 14 Rh 3 I 9 is an inherent property of the 2D intermetallic fragment. Here, the exfoliation of Bi 14 Rh 3 I 9 was performed using two different chemical approaches: (a) through a reaction with n ‐butyllithium and poly(vinylpyrrolidone), (b) through a reaction with betaine in dimethylformamide at 55 °C. The former yielded few‐layer sheets of the new compound Bi 12 Rh 3 I, while the latter led to crystalline sheets of Bi 14 Rh 3 I 9 with a thickness down to 5 nm and edge‐lengths up to several ten microns. X‐ray diffraction and electron microscopy proved that the structure of Bi 14 Rh 3 I 9 remained intact. Thus, it was assumed that the particles are still TIs. Dispersions of these flakes now allow for next steps towards the envisioned applications in nanoelectronics, such as the study of quantum coherence in deposited films, the combination with superconducting particles or films for the generation of Majorana fermions, or studies on their behavior under the influence of magnetic or electric fields or in contact with various materials occurring in devices. The method presented generally allows to exfoliate layers with high specific charges and thus the use of layered starting materials beyond van der Waals crystals.