Electronic and optical properties of armchair silicon carbide nanotubes from first principles

We calculate the electronic band gap and optical spectra of armchair (n, n) silicon carbide nanotubes (n = 9–12) using density functional theory (DFT) combined with Non equilibrium Green's function (NEGF) method as implemented in the SIESTA code. Our simulation suggests that the armchair SiCNTs are indirect-gap semiconductors and SiCNTs (11, 11) have the largest electronic band gap. The z component of the refractive index of SiCNTs (9, 9) reaches its zenith at energies below 2.5 eV. Moreover, the optical absorption takes place in the energy range ∼2−5 eV for the z polarization. The simulated armchair SiCNTs with larger diameter have the smaller first optical band gap as well.