Thickness-dependent structural and growth evolution in relation to dielectric relaxation behavior and correlated barrier hopping conduction mechanism in Ni0.5Co0.5Fe2O4ferrite thin films.

Abstract

Ferrite thin films are explored due to their promising properties, which are essential in various advanced electronic devices. However, depositing a film with pure phase and uniform microstructure is challenging. The Ni_0.5Co_0.5Fe₂O₄ferrite thin films are deposited using pulsed laser deposition technique to explore the effect of thickness on structural properties, growth evolution, temperature-dependent dielectric behavior, and conduction mechanisms. Microstructural analysis revealed that the films are uniformly grown, exhibiting surface roughness ranging from ∼2 to 4 nm. The dielectric response, adhering to a modified Debye model, exhibited multiple relaxation processes, with notable changes in the dielectric constant and loss as film thickness increased. Impedance spectra exhibited both space charge and dipolar relaxation phenomena, corroborated by Cole-Cole and electrical modulus plots. The analysis of the imaginary electric modulus using the Kohlrausch-Williams-Watts function revealed non-Debye-type relaxation in all deposited films, characterized by thermally activated broad peaks. Conductivity decreased up to a certain film thickness, and the frequency exponent derived from Jonscher's power law suggested a correlated barrier hopping model for AC conduction. Activation energies improved with film thickness up to 125 nm, consistent with a constant energy barrier for polarons during relaxation and conduction phases. The film with 125 nm thickness exhibited the optimal dielectric properties, with the maximum dielectric constant, minimum dielectric loss, and highest activation energy. These findings highlight the potential of dense, uniformly grown films with high dielectric constants and low dielectric losses for advanced electronic device applications.