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Defects in silicene: vacancy clusters, extended line defects, and Di-adatoms.

Li S, Wu Y, Tu Y, Wang Y, Jiang T, Liu W, Zhao Y - Sci Rep (2015)

Bottom Line: Here, we present a detailed theoretical study of silicene monolayer containing three types of defects: vacancy clusters, extended line defects (ELDs), and di-adatoms.First-principles calculations, along with ab initio molecular dynamics simulations, revealed the coalescence tendency of small defects and formation of highly stable vacancy clusters.The 5/8/5 ELD - the most favorable extended defect in both graphene and silicene sheets - is found to be easier to form in the latter case due to the mixed sp(2)/sp(3) hybridization of silicon.

View Article: PubMed Central - PubMed

Affiliation: Nano Structural Materials Center, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu, China.

ABSTRACT
Defects are almost inevitable during the fabrication process, and their existence strongly affects thermodynamic and (opto)electronic properties of two-dimensional materials. Very recent experiments have provided clear evidence for the presence of larger multi-vacancies in silicene, but their structure, stability, and formation mechanism remain largely unexplored. Here, we present a detailed theoretical study of silicene monolayer containing three types of defects: vacancy clusters, extended line defects (ELDs), and di-adatoms. First-principles calculations, along with ab initio molecular dynamics simulations, revealed the coalescence tendency of small defects and formation of highly stable vacancy clusters. The 5/8/5 ELD - the most favorable extended defect in both graphene and silicene sheets - is found to be easier to form in the latter case due to the mixed sp(2)/sp(3) hybridization of silicon. In addition, hybrid functional calculations that contain part of the Hatree-Fock exchange energy demonstrated that the introduction of single and double silicon adatoms significantly enhances the stability of the system, and provides an effective approach on tuning the magnetic moment and band gap of silicene.

No MeSH data available.


Silicene structures with one to six vacancies before (left) and after (right) full relaxation.The removed atoms and the rotated bond are shown in red and green, respectively. For each system, the numbers in the parentheses indicate nonhexagonal rings present in the system, where the subscript denotes the number of dangling bonds. For comparison purpose, the formation energy Ef and the formation energy per missing atom Ef′ are also shown in the figure.
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f1: Silicene structures with one to six vacancies before (left) and after (right) full relaxation.The removed atoms and the rotated bond are shown in red and green, respectively. For each system, the numbers in the parentheses indicate nonhexagonal rings present in the system, where the subscript denotes the number of dangling bonds. For comparison purpose, the formation energy Ef and the formation energy per missing atom Ef′ are also shown in the figure.

Mentions: We started by considering all possible configurations for the smaller vacancy clusters (1–3 missing atoms), and the most-likely configurations for the larger clusters (4–6 missing atoms). These vacancy defects were created through removing 1–6 silicon atoms from a pristine lattice. We noticed that even a single vacancy defect could lead to a significant local distortion of silicon's hexagonal arrangement (see Fig. 1a), in agreement with previous literature22. In addition, all considered structures shown in Fig. 1 have higher formation energies, thus less stable, than the pristine silicene.


Defects in silicene: vacancy clusters, extended line defects, and Di-adatoms.

Li S, Wu Y, Tu Y, Wang Y, Jiang T, Liu W, Zhao Y - Sci Rep (2015)

Silicene structures with one to six vacancies before (left) and after (right) full relaxation.The removed atoms and the rotated bond are shown in red and green, respectively. For each system, the numbers in the parentheses indicate nonhexagonal rings present in the system, where the subscript denotes the number of dangling bonds. For comparison purpose, the formation energy Ef and the formation energy per missing atom Ef′ are also shown in the figure.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4306108&req=5

f1: Silicene structures with one to six vacancies before (left) and after (right) full relaxation.The removed atoms and the rotated bond are shown in red and green, respectively. For each system, the numbers in the parentheses indicate nonhexagonal rings present in the system, where the subscript denotes the number of dangling bonds. For comparison purpose, the formation energy Ef and the formation energy per missing atom Ef′ are also shown in the figure.
Mentions: We started by considering all possible configurations for the smaller vacancy clusters (1–3 missing atoms), and the most-likely configurations for the larger clusters (4–6 missing atoms). These vacancy defects were created through removing 1–6 silicon atoms from a pristine lattice. We noticed that even a single vacancy defect could lead to a significant local distortion of silicon's hexagonal arrangement (see Fig. 1a), in agreement with previous literature22. In addition, all considered structures shown in Fig. 1 have higher formation energies, thus less stable, than the pristine silicene.

Bottom Line: Here, we present a detailed theoretical study of silicene monolayer containing three types of defects: vacancy clusters, extended line defects (ELDs), and di-adatoms.First-principles calculations, along with ab initio molecular dynamics simulations, revealed the coalescence tendency of small defects and formation of highly stable vacancy clusters.The 5/8/5 ELD - the most favorable extended defect in both graphene and silicene sheets - is found to be easier to form in the latter case due to the mixed sp(2)/sp(3) hybridization of silicon.

View Article: PubMed Central - PubMed

Affiliation: Nano Structural Materials Center, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu, China.

ABSTRACT
Defects are almost inevitable during the fabrication process, and their existence strongly affects thermodynamic and (opto)electronic properties of two-dimensional materials. Very recent experiments have provided clear evidence for the presence of larger multi-vacancies in silicene, but their structure, stability, and formation mechanism remain largely unexplored. Here, we present a detailed theoretical study of silicene monolayer containing three types of defects: vacancy clusters, extended line defects (ELDs), and di-adatoms. First-principles calculations, along with ab initio molecular dynamics simulations, revealed the coalescence tendency of small defects and formation of highly stable vacancy clusters. The 5/8/5 ELD - the most favorable extended defect in both graphene and silicene sheets - is found to be easier to form in the latter case due to the mixed sp(2)/sp(3) hybridization of silicon. In addition, hybrid functional calculations that contain part of the Hatree-Fock exchange energy demonstrated that the introduction of single and double silicon adatoms significantly enhances the stability of the system, and provides an effective approach on tuning the magnetic moment and band gap of silicene.

No MeSH data available.