Electronic Structure of ZnO/CdX (X= S, Se, Te) Core/Shell Nanowires: DFT Study

A density functional theory (DFT) based computation was conducted to study the electronic band structure, electron density of states (DOS) and partial DOS of ZnO/CdX core/shell nanowires (NWs), where X= S, Se, Te. The band structures calculations show a direct band gap of approximately 1.555 eV, 1.167 eV and 0.833 eV for ZnO/CdS, ZnO/CdSe and ZnO/CdTe, respectively at G-point, using generalized gradient approximation (GGA). The TDOS and PDOS calculations predict that a sharp peak is obtained at -9 eV below the Fermi level, in the valence band (VB) due to the possible hybridization between Zn-s, O-p and X-p orbitals. Also, it was observed that the contributions to the total DOS at the conduction band (CB) are mainly dominated by Zn-s and Cd-s orbitals, hinting at possible strong hybridization between them. Also, the low band gaps of ZnO/CdSe and ZnO/CdTe NWs predict the opacity of these NWs at room temperatures while the relatively high band gap of ZnO/CdS NW could suggest their use in fabrication of high operating voltage devices. Our conjecture hint at the applications of these NWs in devices where selective absorbance is a desired characteristic.