Electronic properties of Janus MoSSe nanotubes

Motivated by the successful experimental approach of Janus MoSSe monolayer, which consists of a Mo layer sandwiched between S and Se atomic layers, we systematically study its nanotube. Its properties are dependent on the tube's diameter, chirality and outer layer. The electronic properties modulated by the strain are also investigated. The results show that armchair MoSSe nanotubes are mainly indirect semiconductors, while zigzag ones are often direct semiconductors. The band gap mainly decreases with the decrease of the diameter. The nanotubes with S outer layers have much smaller band gaps than the ones with Se outer layers. The calculations also show that the MoSSe nanotube with Se outer layer has similar electronic behavior to the MoS2 nanotube, while MoSSe nanotube with S outer layer is quite different from MoS2 nanotube. After applying the external strain, the nanotubes' band gaps mainly increase first and then decrease with the increase of the strain, especially the one with Se outer layer. The semiconductor-to-metal transition could appear in some Janus MoSSe nanotubes by the control of external strain. Our investigations could help to design new electronic devices based on Janus MoSSe nanotubes.