Structural and electronic properties of SiC nanotubes filled with Cu nanowires: A first-principles study

• For Cu5@(8,8) and Cu9@(8,8) systems, the initial shapes are preserved without any visible changes after optimization.
• For Cu13@(8,8) system, a quadraticlike cross-section shape is formed and a relative rotation about common axis is taken place.
• The negative formation energies imply the formation processes of all three Cun@(8,8) systems are exothermic.
• The pristine (8,8) SiCNT is an insulator with a large band gap, but all three Cun@(8,8) systems have a metallic character.
• Considering the maximal metal filling ration in nanotube, we find the Cu9@(8,8) system is top-priority.

The structural and electronic properties of Cun (n=5,9,13) nanowires encapsulated in armchair (8,8) silicon carbon nanotubes (SiCNTs) are investigated using the first principles calculations within the generalized-gradient approximation. We find that the formation processes of these systems are all exothermic. The initial shapes (quadratic–prismatic Cu wire and cylindrical (8,8) SiCNT) are preserved without any visible changes after optimization for the Cu5@(8,8) and Cu9@(8,8) combined systems, but a quadratic-like cross-section shape is formed for the outer nanotube of the Cu13@(8,8) combined system due to the stronger interaction between nanowire and nanotube. The electrons for Si and C atoms in outer SiC sheath affect the electron conductance of the encapsulated metallic nanowire in the Cu13@(8,8) combined system. But in the Cu5@(8,8) and Cu9@(8,8) combined systems, the conduction electrons are distributed only on the copper atoms, so electron transport will occur only through the inner Cu nanowires and the outer inert SiCNTs only function as insulating cable sheaths. Considering the maximal metal filling ratio in nanotube, we know that the Cu9@(8,8) combined system is top-priority in the ultra-large-scale integration (ULSI) circuits and micro-electromechanical systems (MEMS) devices that demand steady transport of electrons.

Optimized structures for (a) Cu5@(8,8), (b) Cu9@(8,8) and (c) Cu13@(8,8) systems, where the yellow, gray and orange balls denote Si, C and Cu, and the big and small balls denote the three type atoms on the adjacent layers A and B, respectively. The numbers m on the orange balls denote the mth Cu shell in the nanowires. For Cu5@(8,8) and Cu9@(8,8) systems, the initial quadratic–prismatic Cu wire and cylindrical (8,8) SiCNT are preserved without any visible changes due to weak Cu–Si and Cu–C bondings. For Cu13@(8,8) system, however, not only a quadraticlike cross-section shape is formed for both nanowire and nanotube but also a relative rotation about their common axis is taken place between nanowire and nanotube due to stronger Cu–C bonding. Figure optionsDownload as PowerPoint slide