Toward the intrinsic limit of topological insulator Bi2Se3
  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. 
Jixia Dai, Damien West, Xueyun Wang, Yazong Wang, Daniel Kwok, S-W.   Cheong, S.B. Zhang, and Weida Wu
cond-mat.mtrl-sci