Tuned electronic, optical and mechanical properties of pristine and hetero nanotubes of group IV elements (C, Si and Ge)

•We studied Electronic and Optical properties of Pristine and Hetero Nanotubes.•The cohesive energy per atom is more for CNT and SiCNT in our study.•Only GeNT is found to be metallic in nature with a conductance of 2G0.•Hetero nanotubes have wide band gap spectrum, hence suitable for electronic devices.•The decreasing order of tensile strength is CNT > SiCNT > GeCNT > SiNT > GeNT > SiGeNT.

Density functional theory has been used to investigate the structural, electronic, optical and mechanical properties of pristine nanotubes of carbon, silicon, germanium and their hetero nanotubes having armchair conformation with chirality (6,6). In the pristine nanotubes it is found that the cohesive energy per atom is more for CNT as compared to other nanotubes under investigation. However, in hetero systems under study its value is highest for SiCNT system and least for GeCNT. GeNT and SiGeNT have been observed to be more puckered in comparison to other systems. All the pristine and heteronanotubes in our study are found to be semiconducting in nature, except GeNT, which is found to be metallic in nature with a conductance of 2G0, indicating GeNT to be an ideal material for ballistic transport. Three different types of hetero nanotubes have wide band gap spectrum which opens up an arena for band gap selective engineered devices. The band gap for SiCNT and GeCNT lie in the visible region, while the band gap for other systems lie in the infrared region. The tuning of electronic band structure by means of compression, tensile strain and external electric field indicates that the band gap can be altered considerably. There is a band gap closure under both compression and expansion at a certain value in all the cases except SiCNT, revealing that its band gap can be varied considerably. The decreasing order of tensile strength is CNT>SiCNT>GeCNT>SiNT>GeNT>SiGeNTCNT>SiCNT>GeCNT>SiNT>GeNT>SiGeNT. The effective mass of holes decreases for pristine systems on the application of compression. Under no strain the effective mass of electrons is generally found to be larger than holes in hetero systems, while it is reverse in pristine systems. In case of unstrained systems, we generally observed that the more the effective mass of electron, the more is the band gap in the corresponding system.

Graphical abstractWe present electronic band structure of pristine and hetero systems under study.Electronic band structure and corresponding total and partial DOS for pristine and heteronanotubes. In the inset we have shown the band structure and density of states for CNT in the vicinity of Fermi energy which shows semi-metallic behaviour.Figure optionsDownload full-size imageDownload as PowerPoint slide