Evaluation of ferric ion molar concentration effect on morphological and opto-electrochemical properties of FexNi1-xO composite thin films

Abstract

The impact of a significantly lower ferric (Fe3+) ion concentration on the structural, morphological, optical, and electrochemical properties of spin-coated FexNi1-xO thin films cast on Indium Tin Oxide (ITO) glasses was scrutinized and then compared with a higher ferric (Fe3+) ion concentration. After a careful structural study of the FexNi1-xO thin films by X-ray diffraction (XRD) analysis, the film surface was further analyzed by atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM) study, and X-ray photoelectron spectroscopy (XPS). Even for a noticeably small amount of substituted Ni2+ metal cations by Fe3+, degradation of the host crystal lattice was surprisingly higher. The influence of Fe3+ ions on the optical properties of FexNi1-xO ITO thin films was studied using UV–visible absorption spectra and Raman spectra. Both unsubstituted and Fe-substituted NiO ITO thin films showed photoluminescence properties. Changes in resistance values in pristine and FexNi1-xO thin films were monitored by an electrochemical impedance spectroscopy (EIS) study. Fe-substituted NiO thin films with a lower molar concentration showed better electrochemical performance as compared to those with a higher molar concentration of Fe3+ ions. This fact was further reinforced through a current-voltage (IV) study and a cyclic-voltagram (CV) study.