Abstract
Antimonene -a single layer of antimony atoms- and its few layer forms are among the latest additions to the 2D mono-elemental materials family. Numerous predictions and experimental evidence of its remarkable properties including (opto)electronic, energetic or biomedical, among others, together with its robustness under ambient conditions, have attracted the attention of the scientific community. However, experimental evidence of its electrical properties is still lacking. Here, we characterized the electronic properties of mechanically exfoliated flakes of few-layer (FL) antimonene of different thicknesses (∼ 2–40 nm) through photoemission electron microscopy, kelvin probe force microscopy and transport measurements, which allows us to estimate a sheet resistance of ∼ 1200 Ω sq−1 and a mobility of ∼ 150 cm2V−1s−1 in ambient conditions, independent of the flake thickness. Alternatively, our theoretical calculations indicate that topologically protected surface states (TPSS) should play a key role in the electronic properties of FL antimonene, which supports our experimental findings. We anticipate our work will trigger further experimental studies on TPSS in FL antimonene thanks to its simple structure and significant stability in ambient environments.
Highlights
Recent works have shown how to produce antimonene and few-layer (FL) antimonene with a variety of different procedures [1,2,3,4,5,6], allowing the exploration of its promising properties [1, 711], including its application in optoelectronics [12,13,14,15]
Antimony does not present a bulk gap, its nonzero topological invariant guarantees the presence of topologically protected surface states (TPSS), coexisting with bulk bands at the Fermi energy [24,25,26]
For a small number of atomic layers, antimonene could already behave as a 3D topological insulator because quantum confinement opens a gap in its bulk bands [27], but, when this occurs, the TPSS on opposite surfaces couple to each other and a gap opens at the Dirac point, partly degrading their topological properties
Summary
Recent works have shown how to produce antimonene and few-layer (FL) antimonene with a variety of different procedures [1,2,3,4,5,6], allowing the exploration of its promising properties [1, 711], including its application in optoelectronics [12,13,14,15]. A minimum of approximately 7-8 layers (∼ 3 nm) is needed for a full decoupling of the TPSS on opposite surfaces [25, 28], but bulk bands already cross the Fermi energy at this small thickness [26, 27] In this sense, FL antimonene is not so different from actual 3D topological insulators where the contribution of bulk bands at the Fermi energy is difficult to eliminate. We present a local morphological and electronic study of mechanically exfoliated FL antimonene flakes of thicknesses between ∼ 2 and 40 nm (see Methods) Within this thickness range, the band structure fully reveals the decoupling of the top and bottom TPSS and the bulk bands present a finite contribution at the Fermi energy
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