OPTO-ELECTRONIC PROPERTIES OF NICKEL OXIDE: A DFT STUDY

Abstract

Nickel oxide is a compound of significant scientific value due to its chemical, electrical, and optical properties. NiO seems to be of special relevance as a prototype material for Transparent conducting materials and also for sensor applications. Nickel oxide can be easily produced using a variety of processes, including chemical deposition, evaporation, nickel oxidation, sputtering and many more. Nickel oxide films often have nonstoichiometric qualities. Due to this nonstoichiometry, the various properties of nickel oxide films fluctuate. In various applications, these typical changes in properties will have different implications. However, even with minor variations, these qualities frequently differ significantly. Finding the proper composition experimentally is thus often a difficult undertaking. That is why we typically use computational techniques to assist us in the search. Density functional Theory (DFT) is a widely used computational Technique to study the electronic properties of materials, It can be also used to determine other derivative properties using various approximation. However, NiO being a Transition metal oxide conventional DFT often fail in predicting the behavior of this class of compounds. So, in this study DFT +U calculations are done on various type of NiO samples to study the variance of optical and electronic properties of NiO with changes in composition of sample. From the results of the study, we observe that in order to improve the electrical properties of NiO, the common methods often employed deteriorates the optical properties. we studied how vacancies affect the opto-electronic properties of the solid qualitatively and quantitatively. The oxygen vacancies created defects states in between the conduction band, thus deteriorating the optical properties. While the nickel vacancies showed slight promise for creating a desirable material, there were some concerns due to the appearance of half metallic nature in those samples. On increasing the nickel vacancies, we observe that the earlier observed Half metallic nature deteriorates the optical properties of NiO even further. It also seems that the sample degrades relatively faster with these vacancies. Then we looked into possible doping to be done to NiO so as to remedy the drawback of instability of native vacancy defects. Trace doping studies were done with Cu and Zn. The doping of copper seems to improve the electric properties.