First-principles study of the formation of single-walled SiC nanotubes from bilayered SiC ribbons

In this paper, we demonstrate by employing first-principles density functional theory calculations that AB or Bernal-type stacked armchair and AB' zigzag bilayered SiC nanoribbons are converted into defect-free zigzag (zz) and armchair (ac) single-walled SiC nanotubes (SiCNTs), respectively. This formation of closed SiC nanostructures is facilitated by the establishment of interlayer bonds and the compensation of different polarity of charges at their edges. It is also understood from nudged elastic band calculations that edge dynamics is involved in the formation of SiCNTs, and growing zz-SiCNTs is found to be more feasible as compared with ac-SiCNTs. Our study of dimension-dependent electronic properties shows that both of these SiCNTs are semiconducting in nature, as the edge states of the nanoribbons have completely vanished. On the other hand, AA stacked zz bilayered SiC nanoribbons are converted into defective ac-SiCNTs, but conducting edge states are preserved owing to the presence of Si-Si and C-C bonds. Finally, we explore the critical dimension for the formation of SiCNTs. This reveals that freestanding and defect-free SiCNTs could be formed from nanoribbon with a diameter up to 1.2 nm, above which the closed edge structure possibly evolves.