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.
Highlights
Transition metal oxides (TMOs) establish an important section of semiconducting materials which exhibit a variety of electronic and magnetic properties that depend on the nature of their respective outer d-shell configurations [1]
Density functionaltheory (DFT) study on undoped NiO was first reported in detail in [1], wherein the electron correlations in the 3d shell of metal ions in nickel oxide were computed using a combination of local spin density approximation (LSDA) and unrestricted Hartree-Fock approximation (U) techniques
All of the computations are performed based on the generalized gradient (GGA) and local density approximations (LDA) to DFT using the Vienna ab initio simulation package (VASP) [41,42,43]. 4 k-points in the irreducible part of the Brilliouin zone is a result of test of convergence in the 32-atom primitive
Summary
Transition metal oxides (TMOs) establish an important section of semiconducting materials which exhibit a variety of electronic and magnetic properties that depend on the nature of their respective outer d-shell configurations [1]. Density functionaltheory (DFT) study on undoped NiO was first reported in detail in [1], wherein the electron correlations in the 3d shell of metal ions in nickel oxide were computed using a combination of local spin density approximation (LSDA) and unrestricted Hartree-Fock approximation (U) techniques. Recent studies indicate an enormous work in doped NiO to enhance room temperature ferromagnetism for multiferroic devices [30], supercapacitor applications [31], and resistive switching [32] Dopants, such Cu [32] and Li [33] enhance the p-type conductivity of NiO films and have been studied extensively, both theoretically and experimentally. We study the effect of doping Pd and Pton the bandgap of NiO by varying doping concentrations from 0 to 25% in a 32 atom NiO
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