Optoelectronic Properties and Energetics of Defects and Impurities in NiO Studied Using Ab Initio Calculations

Abstract

Nickel oxide (NiO) is a transparent conducting oxide (TCO) which has shown potential for applications in the next generation of memristors for non­volatile resistive RAM (RRAM), solar cells, spintronics, and other devices. Thus it is of interest to study the intrinsic defects responsible for this resistive switching mechanism as well as other impurities in order to improve desired characteristics. Density Functional Theory (DFT) based ab initio calculations are used to study the electronic and optical properties as well as the energetics and stability of defects and impurities when introduced into rock-­salt NiO. Exchange­-correlation effects were included in the calculations within the generalized gradient approximation where to better describe the d­-orbitals of Ni and transition metal (TM) dopants a Hubbard potential U contribution was added (GGA+U). Results also considering a hybrid functional (HSE06) to treat the exchange correlation are shown for both the pristine and altered systems. NiO systems containing defects and impurities were studied using supercell grown along the [111] direction of 32 atoms to simulate the anti­ferromagnetic (AFM) configurations. Stability was investigated through the calculation of formation energies of these systems in order to discern what is most energetically favorable.