Electronic and optical characteristics of phosphorus-doped carbon nanotubes: a first principle study

The electronic and optical properties of pure, phosphorus doped infinite and finite single walled carbon nanotubes (n, 0) (n = 4, 5 and 6) with different doping degree were investigated with the combination of density functional theory (DFT) and Non-Equilibrium Green's function (NEGF) formalisms at room temperature. It was found that depending on the chirality, phosphorus atoms may eliminate the Van Hove Singularity energy or increase the density of states (DOS) at Fermi level. Also, replacing the carbons by phosphorus atoms increases DOS at Fermi level. The π bonds between carbon and phosphorus are responsible for extraordinary DOS at Fermi level as well. Moreover, each P atom in the simulated tubes contains about 2.62e-2.94e. Replacing carbon atoms by phosphorus eventuates in the reduction of optical susceptibility and the statics refractive index. Last but not least, despite pure SWCNTs, the doping results in the lower static refractive index as well as the increment of an intraband optical gap for the parallel to tube axis polarization through P-SWCNTs.