Abstract
Using scanning tunneling spectroscopy and theoretical simulations we have studied the effects of nitrogen gas exposure on the electronic density of states of Bi2Se3, a well-studied topological insulator. In carefully controlled measurements, Bi2Se3 crystals were initially cleaved in a helium gas environment and then exposed to a 22 SCFH flow of ultra-high purity N2 gas. We observe a resulting change in the spectral curves, with the exposure effect saturating after approximately 50 min, ultimately bringing the Dirac point about 50 meV closer to the Fermi level. These results are compared to density functional theory calculations, which support a picture of N2 molecules physisorbing near Se vacancies. Furthermore, ab initio molecular dynamics simulations aided by a Blue Moon ensemble method reveal the dissociative adsorption of N2 molecules which then bind strongly to Se vacancies at the surface. In this scenario, the binding of the N atom to a Se vacancy site removes the surface defect state created by the vacancy and changes the position of the Fermi energy with respect to the Dirac point.
Original language | English (US) |
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Article number | 115012 |
Journal | Solid State Communications |
Volume | 359 |
DOIs | |
State | Published - Jan 1 2023 |
Funding
The experimental work presented in this paper was supported by the U.S. Department of Energy , Basic Energy Sciences , under Award DE-SC0017888 . Computational resource was provided by the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under Contract No. DE-AC02-05CH11231. At Argonne National Laboratory samples synthesis and characterization were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering .
Keywords
- Chemisorption
- Density functional theory
- Dissociative adsorption
- Physisorption
- Scanning tunneling microscopy
- Topological insulator
- ab initio molecular dynamics
ASJC Scopus subject areas
- General Chemistry
- Condensed Matter Physics
- Materials Chemistry