A Computational Study on the Variation of Bandgap Due to Native Defects in Non-Stoichiometric NiO and Pd, Pt Doping in Stoichiometric NiO

Abstract

This paper presents a computational study of non-stoichiometric nickel oxide in a 64-cell NiO system to model and validate localized heating effects due to nanosecond laser irradiation. Variation in the Bandgap of NiO is studied as a function of varying concentrations of native defects, ranging from 0 to 25%. It is observed that there is a slight increase in the bandgap from 3.80eV for stoichiometric NiO to 3.86eV for Ni-rich NiO and to 3.95eV for O-rich NiO. It is hence deduced that the experimental laser irradiation leads to simultaneous reduction of Ni2+ ions and the oxidation of NiO as the number of laser pulses increase. As well, a detailed study on the effects of doping nickel family elements, i.e., palladium (Pd) and platinum (Pt), in stoichiometric NiO is presented. A bandgap decrease from 3.8eV for pure NiO to 2.5eV for Pd-doping and 2.0eV for Pt-doping for varying doping concentrations ranging from 0–25% Pd, Pt, respectively,is observed.