Tight-binding description of optoelectronic properties of silicon nanotubes

Using a tight-binding model up to the second nearest-neighbor (2NN) interactions, an analytic expression for the selection rule and the optical dipole matrix elements have been derived as a function of optical energy of some single-walled silicon hexagonal nanotubes (Si h-NTs). For this purpose, the energy dispersion, dipole matrix elements and optical absorption obtained up to the 2NN are compared with those obtained for the first nearest-neighbors (1NN) for incident light polarized parallel to the tube axis. By concerning more distant-neighbors, in general, the 1NN model can be improved. The results show that there is a shift in the dispersion energy including second neighbors in comparison with first neighbors, which it depends on the subband index. One can also see that the absorption intensity is increased for both metallic and semiconducting nanotubes. The numerical result may be useful in designing nano-optoelectronic devices.