First principles band gap engineering of [1 1 0] oriented 3C-SiC nanowires

Silicon carbide nanowires offer excellent opportunities for technological applications under harsh environmental conditions, however, the 3C-SiC polytype nanowires, grown along the [1 1 0] crystallographic direction, have been rarely studied, as well as the effects of the surface passivation on their physical properties. This work addresses the effects of hydrogen passivation on the electronic band gap of silicon carbide nanowires (SiCNWs) grown along the [1 1 0] direction by means of Density Functional Theory. We compare the electronic properties of fully hydrogen-passivated SiCNWs in comparison to those of SiCNWs with a mixed passivation of oxygen and hydrogen by changing some of the surface dihydrides with Si–O–Si or C–O–C bonds. The results show that regardless of the diameter and passivation, most of the nanowires have a direct band gap which suggests an increased optical activity. The surface C–O–C bonds reduce the electronic band gap energy compared to that of the fully H-terminated phase, while the nanowires with Si–O–Si bonds have a larger band gap. The calculation of formation energies shows that the oxygen increases the chemical stability of the SiCNWs. These results indicate the possibility of band gap engineering on SiC nanostructures through surface passivation.