Paper detail

Study of morphology effects on magnetic interactions and band gap variations for 3$d$ late transition metal bi-doped ZnO nano structures by hybrid DFT calculations

Using density functional theory (DFT) based electronic structure calculations, the effects of morphology of semiconducting nano structures on the magnetic interaction between two magnetic dopant atoms as well as a possibility of tuning band gaps have been studied in case of the bi-doped (ZnO)$_{24}$ nano structures with the impurity dopant atoms of the 3$d$ late transition metals (TM) - Mn, Fe, Co, Ni and Cu. To explore the morphology effect, three different structures of the host (ZnO)$_{24}$ nano-system having different degrees of spatial confinement, have been considered : a two dimensional (2D) nanosheet, an one dimensional (1D) nanotube and a finite cage-shaped nanocluster. The present study employs hybrid density functional theory to accurately describe the electronic structure of all the systems. It is shown here that the magnetic coupling between the two dopant atoms, remains mostly anti-ferromagnetic in course of changing the morphology from the sheet geometry to the cage-shaped geometry of the host systems, except for the case of energetically most stable bi-Mn doping, which shows a transition from ferromagnetic to anti-ferromagnetic coupling with decreasing aspect ratio of the host system. The effect of the shape change, however, has a significant effect on the overall band gap variations of both the pristine as well as all the bi-doped systems, irrespective of the nature of the dopant atoms and provides a means for easy tunability of their optoelectronic properties.