Toward the intrinsic limit of topological insulator Bi2Se3

TL;DR

This study combines microscopy and calculations to identify native defects in Bi2Se3, revealing their impact on bulk conduction and showing that controlled synthesis can approach the material's intrinsic electronic limit.

Contribution

It provides a detailed defect analysis in Bi2Se3 and demonstrates how growth kinetics influence defect levels, enabling near-intrinsic electronic properties without extrinsic doping.

Findings

Native defects cause bulk conduction and potential fluctuations.

Defect concentrations exceed thermodynamic limits due to growth kinetics.

Optimized synthesis achieves Fermi level inside the band gap.

Abstract

Combining high resolution scanning tunneling microscopy and first principle calculations, we identified the major native defects, in particular the Se vacancies and Se interstitial defects that are responsible for the bulk conduction and nanoscale potential fluctuation in single crystals of archetypal topological insulator Bi2Se3. Here it is established that the defect concentrations in Bi2Se3 are far above the thermodynamic limit, and that the growth kinetics dominate the observed defect concentrations. Furthermore, through careful control of the synthesis, our tunneling spectroscopy suggests that our best samples are approaching the intrinsic limit with the Fermi level inside the band gap without introducing extrinsic dopants.