Catalyst-free vapour–solid technique for deposition of Bi₂Te₃and Bi₂Se₃nanowires/nanobelts with topological insulator properties

Abstract

We present a simple two-stage vapour-solid synthesis method for the growth of bismuth chalcogenide (Bi2Te3, Bi2Se3) topological insulator nanowires/nanobelts by using Bi2Se3 or Bi2Te3 powders as source materials. During the first stage of the synthesis process nanoplateteles, serving as "catalysts" for further nanowire/nanobelt growth, are formed. At a second stage of the synthesis, the introduction of a N2 flow at 35 Torr pressure in the chamber induces the formation of free standing nanowires/nanobelts. The synthesised nanostructures demonstrate a layered single-crystalline structure and Bi : Se and Bi : Te ratios 40 : 60 at% for both Bi2Se3 and Bi2Te3 nanowires/nanobelts. The presence of Shubnikov de Haas oscillations in the longitudinal magneto-resistance of the nanowires/nanobelts and their specific angular dependence confirms the existence of 2D topological surface states in the synthesised nanostructures.

Vapor–solid synthesis and enhanced thermoelectric properties of non-planar bismuth selenide nanoplates on graphene substrate

“…From the obtained data, it can be assumed that during the first stage of synthesis process, when there was no gas flow introduced into the furnace tube, the growth of planar hexagonal nanoplates occurred similarly to our previous report [19], what resulted in formation of heteroepitaxial structure with graphene [4]. The difference with the previous report [19] arose during the second stage of the synthesis process, when the temporary gas flow was introduced into the furnace tube.…”

“…4a, b) illustrate the atomic structure of the nanoplates. The inner areas of the nanoplates are single-crystalline, while the edges of the nanoplates/nanoplate terraces are covered with amorphous native oxide layer, which is a result of rapid Bi 2 Se 3 oxidation under ambient conditions [18,19,29].…”

“…Non-planar bismuth selenide nanoplates and coatings were synthesized on monolayer graphene substrates by previously reported by our group twostage catalyst-free vapor-solid deposition method [19]. The synthesis was carried out in a high-temperature vacuum furnace (GCL-1100X, MTI Corp.).…”

“…However, despite the demonstrated deposition of Bi 2 Se 3 coatings consisting of randomly oriented nanostructures on variety of substrates as glass, quartz, and indium-tin-oxide (ITO) glass [17][18][19], the growth of non-planar nanoplates on the graphene still remains a challenging task due to mentioned above very small mismatch between the lattice constants of bismuth selenide and graphene, promoting epitaxial growth of the nanoplates. To our knowledge, there are no reports on growth of non-planar bismuth selenide or telluride nanoplates on the graphene substrates.…”

“…This work is focused on synthesis of non-planar bismuth selenide separate nanoplates and consisting of combination of planar and non-planar nanoplates continuous coatings (further in text-non-planar coating) on graphene substrates, employing recently reported by our group catalyst-free two-stage vaporsolid process [19] for synthesis of bismuth selenide and bismuth telluride nanowires/nanobelts. The thermoelectric performance and sensing of infrared illumination of non-planar coatings enclosed in layered graphene/Bi 2 Se 3 /graphene devices was investigated and compared with thermoelectric properties of Bi 2 Se 3 coatings consisting of only planar coalescent nanoplates (further in text-planar coating).…”