Dumbbell configuration of silicon adatom defects on silicene nanoribbons

Quoc Duy Ho,Ong Kim Le,Truong Quoc Tuan,Huynh Anh Huy,Nguyen Le Hoai Phuong

doi:10.1038/s41598-021-93465-5

Abstract

Using density functional theory (DFT), we performed theoretical investigation on structural, energetic, electronic, and magnetic properties of pure armchair silicene nanoribbons with edges terminated with hydrogen atoms (ASiNRs:H), and the absorptions of silicon (Si) atom(s) on the top of ASiNRs:H. The calculated results show that Si atoms prefer to adsorb on the top site of ASiNRs:H and form the single- and/or di-adatom defects depending on the numbers. Si absorption defect(s) change electronic and magnetic properties of ASiNRs:H. Depending on the adsorption site the band gap of ASiNRs:H can be larger or smaller. The largest band gap of 1 Si atom adsorption is 0.64 eV at site 3, the adsorption of 2 Si atoms has the largest band gap of 0.44 eV at site 1-D, while the adsorption at sites5 and 1-E turn into metallic. The formation energies of Si adsorption show that adatom defects in ASiNRs:H are more preferable than pure ASiNRs:H with silicon atom(s). 1 Si adsorption prefers to be added on the top site of a Si atom and form a single-adatom defect, while Si di-adatom defect has lower formation energy than the single-adatom and the most energetically favorable adsorption is at site 1-F. Si adsorption atoms break spin-degeneracy of ASiNRs:H lead to di-adatom defect at site 1-G has the highest spin moment. Our results suggest new ways to engineer the band gap and magnetic properties silicene materials.

Highlights

Defects in a material are almost unavoidable in the fabrication and processing, and sometimes, they are introduced through the synthesize procedure purposively for controlling some specific a pplications[20,21]
We performed with density functional theory used the Vienna Ab-initio Simulation Package (VASP 5.4.4), the projector augmented wave method (PAW)[25], and the Generalized Gradient Approximation (GGA) or Perdew, Burke, and Ernzerh (PBE)[26] for exchange and correlation
The ASiNRs:H and ASiNRs:H adatom(s) defect band structures calculations were calculated in supercells (64 atoms for pure ASiNRs:H) with a vacuum space of around 15 Å to avoid the interaction between the nanoribbon and its periodic images

Summary

Computational details

We performed with density functional theory used the Vienna Ab-initio Simulation Package (VASP 5.4.4), the projector augmented wave method (PAW)[25], and the Generalized Gradient Approximation (GGA) or Perdew, Burke, and Ernzerh (PBE)[26] for exchange and correlation. The plane-wave basis set was truncated at 420 eV and the kinetic energy cut-off for the augmentation charges was 840 eV. The convergence condition of 1 0–4 eV was applied for the self-consistent electronic energy and the relaxation of all ions was carried out until the force on each ion was smaller than 0.02 eV/Å. The structure optimizations were carried out with a 1 × 1 × 3 approximations for the Brillouin zone sampling, where 3 is only applied for the periodic direction. Convergence of the k-point sampling was checked again by applying a 1 × 1 × 5 set. V ESTA328 was used to display the balls and stick structure models of ASiNRs:H in Figs. 1 and 3

Results and discussions

Conclusion

Additional information