Electronic and optical properties of Na, Mg, and Al substituted Zinc-oxide Nanotube: An insight DFT study

Background: The present work deals with DFT-based theoretical investigations on pristine and metal (M = Na, Mg, and Al) substituted zinc oxide nanotube (M-ZnONT). The investigation advocates a change in the electronic bandgap of ZnONT on the respective substitution of Zn with Na, Mg, and Al. The forbidden energy gap vanishes on Na incorporation, while Al substitution brings the gap to 0.08eV. The formation energy calculations suggest the feasibility of these metallic substitutions, of which Na incorporation is most favorable. Partial density of state (PDOS) analysis is well correlated with band structures. A localized state above the Fermi level contributed from Al-3p in Al-ZnONT suggests the electronic affinity of Al-ZnONT for incoming nucleophiles. Our optical investigation shows large ε1(ω) values in far-infrared (IR) and visible (Vis) regions for M-ZnONT. Hence, suggests a high refractive index for the metal-substituted ZnONTs in the prescribed range. The study suggests that photonic energy loss due to attenuation, bending, and absorption are weak in ultra-violet (UV) and far UV regions i.e, (3eV to 8eV). However, for the respective energy range, high reflectivity is predicted. This indicates the nanotubes as a good reflector for the purpose of coating material surfaces where high reflection is demanded. Objective: Finding electronic and optical properties of functionalized ZnONT using DFT method. Methods: All calculations have been performed in the framework of density functional theory (DFT) using Troullier Martins’s norm-conserving pseudo-potential. Results: Metal incorporation at the surface of ZnONT consequent intense ε1(ω) values in far infra-red and visible regions for M-ZnONT. Conclusion: The investigation suggests that the metal-substituted nanotube is a good reflector for coating material surfaces where high reflection is demanded.