Band Bending Inversion in Bi₂Se₃ Nanostructures

Abstract

Shubnikov-de Haas oscillations were studied under high magnetic field in Bi2Se3 nanostructures grown by chemical vapor transport, for different bulk carrier densities ranging from 3 × 10(19) cm(-3) to 6 × 10(17) cm(-3). The contribution of topological surface states to electrical transport can be identified and separated from bulk carriers and massive two-dimensional electron gas. Band bending is investigated, and a crossover from upward to downward band bending is found at low bulk density as a result of a competition between bulk and interface doping. These results highlight the need to control electrical doping both in the bulk and at interfaces in order to study only topological surface states.

Weakly-coupled quasi-1D helical modes in disordered 3D topological insulator quantum wires

“…Due to a high density of Se vacancies acting as donors, these nanostructures are metallic, with the surface Fermi energy E F lying about 250 meV above the Dirac point. The total conductance results from a comparable contribution from surface and bulk carriers, as inferred from classical magneto-resistance and transconductance measurements on wide nanoribbons3132, but conductance fluctuations in long wires are dominated by topological surface states, as shown below (see also Supplementary Informations: I). For helical Dirac fermions in the narrow Bi 2 Se 3 wires considered here, the energy level spacing Δ ≈ 6 meV gives N  ≈ 2 E F /Δ ≈ 80 transverse modes, and we find l tr  < 300 nm, using v F  ≈ 5 · 10 5  ms −1 obtained from angle-resolved photoemission spectroscopy333435 (see Supplementary Informations: II-D).…”

“…One chamber contains a Bi 2 Se 3 or Bi 2 Te 3 powder (Sigma-Aldrich) and the other a p ++ -Si/SiO x substrate. Electrical properties of wide ribbons were studied in high magnetic fields32 or using an electrical back gate31. Individual nanostructures were imaged with a scanning electron microscope, and their height was measured by atomic force microscopy.…”

In-plane topological p-n junction in the three-dimensional topological insulator Bi2−xSbxTe3−ySey

“…Consequently, equation (2) gives an asymmetric structure in the R xx − V G curve. In the case of pristine BSTS, the Fermi level is also different between the top and the bottom surfaces owing to the charge transfer from the substrate46. In addition, the n-type trivial surface accumulation layer may be suppressed under the negative V G .…”

Determination of the energy band gap of Bi2Se3

“…g ., refs 6 and 7 This technique thus seems to be well-suited for investigations of surface properties and the observation of conical bands on the surface of topological insulators is definitely one of its greatest achievements 28 . At the same time, the visualization of a truly bulk electronic band structure, especially in narrow gap materials, which are characterized by pronounced band bending effects 29 and charge accumulation layers on the surface, may be a challenging task for the surface-sensitive techniques, with a strongly limited penetration depth.…”