Optical Transition of Zigzag Silicon Nanotubes Under Intrinsic Curvature Effect

Theoretical studies on the electronic and optoelectronic properties of silicon hexagonal nanotubes (Si-h NTs) are carried out in the low energy region by including the effect of intrinsic geometry curvature. The effect of curvature changes the hopping matrix between nearest sites in the tube. Based on the tight-binding method in the nearest-neighbor approximation and electric-dipole vector, we obtain an analytical expression for optical matrix elements as a function of wavevector and subband index for the incident polarized light parallel to the tube axis. Our results show that the degeneracy of the bands is broken by introducing the curvature effect in the calculations leading to a change in the transition dipole matrix. Also, the resonance peaks in the absorption spectrum and the maximum absolute values in the dipole matrix elements of the tubes appear in the Van-Hove singularities for each band. Our results provide the fundamental information for developing new designs of nano- electronic and nano- optoelectronic devices.