Abstract
In the present work, a catalyst-free physical vapour deposition method is used to synthesize high yield of Bi2Se3 nanoribbons. By replacing standard glass or quartz substrates with aluminium covered with ultrathin porous anodized aluminium oxide (AAO), the number of synthesized nanoribbons per unit area can be increased by 20–100 times. The mechanisms of formation and yield of the nanoribbons synthesized on AAO substrates having different arrangement and size of pores are analysed and discussed. It is shown that the yield and average length of the nanoribbons can base tuned by adjustment of the synthesis parameters. Analysis of magnetotransport measurements for the individual Bi2Se3 nanoribbons transferred on a Si/SiO2 substrate show the presence of three different populations of charge carriers, originating from the Dirac surface states, bulk carriers and carriers from a trivial 2DEG from an accumulation layer at the Bi2Se3 nanoribbon interface with the substrate.
Highlights
The TI properties of Bi2Se3 have been mostly investigated by measurements on cleaved surfaces of bulk crystals[4] and molecular beam epitaxy (MBE) synthesized thin films[5]
Estimation from the low magnification scanning electron microscope (SEM) images of the Bi2Se3 nanostructures grown on glass and anodized aluminium oxide (AAO) surfaces (Fig. 2) revealed that the number of the nanoribbons per unit area grown on the AAO surfaces where www.nature.com/scientificreports nanopores have distinct asperities between them (Fig. 1a right panel, Fig. 2c,d), is 20–100 times higher in comparison to the AAO substrates with no distinct asperities (Fig. 1b right panel, Fig. 2a) and the glass substrates (Fig. 2b)
Previous studies on Bi2Se3 nanoribbons grown on glass substrates by a similar physical-vapour deposition (PVD) approach as we report here, have shown a multi-band transport, with carriers from topological surface states at the nanoribbon top surface, bulk carriers and trivial carriers from a 2DEG accumulation layer at the interface between the nanoribbon bottom surface and the substrate of Si/SiO214
Summary
The TI properties of Bi2Se3 have been mostly investigated by measurements on cleaved surfaces of bulk crystals[4] and molecular beam epitaxy (MBE) synthesized thin films[5] It was realised, that the residual (native) doping arising from the Se vacancies in as-synthesized Bi2Se36 is the main obstacle for a direct investigation of the fundamental properties of topological surface states, and requires additional treatment to minimize dominance of the bulk transport. A drawback of the nanoribbon fabrication by catalyst-free PVD technique is the relatively low yield of the nanoribbons. The nanoribbons grown by these methods may be doped by catalyst atoms This may result in increased bulk carrier density screening the transport properties from the topological surface states
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