A Computational Study of the Properties of Pure, Adsorbed, and Doped Zinc Oxide With Copper and Nickel Atoms

Zinc oxide (ZnO), a promising n-type semiconductor with hexagonal-layered structure, has attracted significant attention due to its versatile applications in optical and electronic devices, including field-effect transistors, nanogenerators, LEDs, laser diodes, and solar cells. Despite extensive research on pure ZnO, the effects of doping with transition metals like copper (Cu) and nickel (Ni) on its electronic properties remain underexplored. This study investigates the electronic properties of pure ZnO, ZnO doped with Cu and Ni, and ZnO co-doped with Cu and Ni using Density Functional Theory (DFT) and the GGA-PBE approximation (CASTEP). Results reveal that Cu and Ni preferentially adsorb above oxygen sites on the ZnO surface, altering its electronic structure. Pure ZnO exhibited a band gap of 1.68 eV with a bond length of 1.89 Å. Upon Cu adsorption, the gap reduced to 0.11 eV with a bond length of 1.97 Å, while Ni adsorption resulted in a 0.862 eV gap and a 2.03 Å bond length. Doping ZnO with Cu eliminated the band gap, making it conductive with a bond length of 1.888 Å, whereas Ni doping narrowed the gap to 0.369 eV with a bond length of 1.85 Å. These findings underscore the potential of Cu- and Ni-doped ZnO for enhanced electronic applications by tuning the band gap, paving the way for advances in nanoscale device engineering.