Abstract
Using first-principles method within the framework of the density functional theory, we study the influence of native point defect on the structural and electronic properties of Bi2Se3. Se vacancy in Bi2Se3 is a double donor, and Bi vacancy is a triple acceptor. Se antisite (SeBi) is always an active donor in the system because its donor level (ɛ(+1/0)) enters into the conduction band. Interestingly, Bi antisite (BiSe1) in Bi2Se3 is an amphoteric dopant, acting as a donor when μe < 0.119 eV (the material is typical p-type) and as an acceptor when μe > 0.251 eV (the material is typical n-type). The formation energies under different growth environments (such as Bi-rich or Se-rich) indicate that under Se-rich condition, SeBi is the most stable native defect independent of electron chemical potential μe. Under Bi-rich condition, Se vacancy is the most stable native defect except for under the growth window as μe > 0.262 eV (the material is typical n-type) and ΔμSe < −0.459 eV (Bi-rich), under such growth window BiSe1 carrying one negative charge is the most stable one.
Highlights
The narrow-band-gap semiconductor Bi2Se3 (Eg ∼ 0.35 eV)[1,2] has been best known for a long time as an excellent thermoelectric material because of their unique near-gap electronic structure and high thermoelectric figure of merit.[3,4,5] Recently, with the research development of topological insulators(TIs),[6,7,8,9] it attracts the geeat attention again
Our calculations are performed in a 3 × 3 × 1 supercell with 135 atoms by using the plane-wave pseudopotential code Vienna ab initio simulation package (VASP).[29,30]
Our results show that the stable charge states of VSe1 in Bi2Se3 V+Se11 and V0Se1 as the Fermi level moves through the bandgap, which indicates that VSe1 are V+Se21, acts as a double donor in the systems
Summary
The narrow-band-gap semiconductor Bi2Se3 (Eg ∼ 0.35 eV)[1,2] has been best known for a long time as an excellent thermoelectric material because of their unique near-gap electronic structure and high thermoelectric figure of merit.[3,4,5] Recently, with the research development of topological insulators(TIs),[6,7,8,9] it attracts the geeat attention again. TI is a new state having an energy gap in its bulk band structure and metallic helical states on its surface, which distinct from simple a metal or an insulator.[10,11] Bi2Se3 is a strong three dimensional (3D) topological insulator with its surface states consisting of single Dirac cone at the point which is protected by the time-reversal symmetry from any time-reversal perturbation, such as crystal defects and nonmagnetic impurities.[10,12,13]. It needs well-defined electrical and thermal conductivities, high mobility of free current carriers, and thermoelectric power, all of them will be influenced by the presence of native defects.[15,16,17] As a topological insulator, the intrinsic defects such as antisites or vacancies behave as n type dopant and shift the Fermi level above the Dirac point, which makes it difficult to characterize the topological transport properties.[13,18,19,20]
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