Effect of Mg substitution in delafossite structured CuFeO2 thin film deposited on FTO coated glass substrate and its diode characteristics

Abstract

In an attempt to introduce delocalized electronic states in the valance band of p-type delafossite crystals of CuFeO2, substitution with Mg in its lattice has been done in this work. The delafossite type crystal structure has been achieved at a comparatively low temperature of 723K through the simple chemical process of sol-gel spin coating technique. It was deposited on Florine doped tin oxide (FTO) coated glass substrate and subsequently studied with X-ray diffraction (XRD) measurement, transmission electron microscopic (TEM) measurement, atomic force microscopic (AFM) measurements, X-ray photoelectron spectroscopy (XPS). The structural, morphological, compositional, optical and electrical properties of the Mg doped CuFeO2/FTO heterostructure as investigated in this work, show significant development and response with Mg doping concentration. The density functional calculations also indicate such effects upon Mg substitution, arising from impurity of Mg 3s state, created near the upper edge of the valence band along with a shift in the Fermi level towards the valence band. The hole-doping by Mg2+ substituting Fe3+ enhances the quantum fluctuations and bond disorder providing enhanced p-type conductivity. Most importantly the heterostructure shows excellent diode like rectifying character in the current-voltage (I-V) plot and significantly modified under Mg doping concentrations. Chemically stable, environment friendly, p-type semiconductor material of CuFeO2 with improved functionality through Mg substitution will find its significant place in recent development of semiconductor processing technology.