Band bending inversion in Bi$_2$Se$_3$ nanostructures

TL;DR

This study investigates band bending inversion in Bi$_2$Se$_3$ nanostructures, revealing how doping levels influence surface and bulk electronic states, crucial for isolating topological surface states.

Contribution

It demonstrates the transition from upward to downward band bending in Bi$_2$Se$_3$ nanostructures based on bulk doping levels, highlighting the importance of doping control.

Findings

Band bending crossover observed at low bulk density

Separation of surface states from bulk carriers achieved

Doping control is essential for studying topological surface states

Abstract

Shubnikov-de-Haas oscillations were studied under high magnetic field in Bi$_2$Se$_3$ nanostructures grown by Chemical Vapor Transport, for different bulk carrier densities ranging from $3\times10^{19}\text{cm}^{-3}$ to $6\times10^{17}\text{cm}^{-3}$. 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.