Effect of thickness on the electronic structure, charge transport and magnetic properties of CuO:Fe thin films

Abstract

In this work, the structural, optical, electrical, and magnetic properties of Fe-doped CuO thin films deposited by thermal evaporation with different thicknesses were investigated. X-ray diffraction (XRD) analyses revealed the formation of a single CuO phase, while Raman spectroscopy measurements confirmed the characteristic monoclinic structure of CuO. From an optical perspective, an increase in both the bandgap energy and Urbach energy was observed with decreasing film thickness, indicating changes associated with the electronic structure and degree of disorder of the system. Electrical transport measurements revealed a transition in the dominant charge-carrier type, from p-type conduction in the thinner films to n-type conduction as the film thickness increased, which is associated with the activation of Fe³⁺ substitutions and the generation of intrinsic defects. Regarding the magnetic properties, the films exhibited room-temperature ferromagnetic behavior, with a magnetization of 1.1 emu/g. The magnetization decreased with decreasing film thickness, which is attributed to the change in the oxidation state of Cu²⁺ to Cu⁺. Additionally, the magnetic susceptibility measurements showed a dependence of the blocking temperature on film thickness, with an increase in the blocking temperature as the crystallite size increased. These results demonstrate a strong dependence of the optical, electrical, and magnetic properties of CuO:Fe thin films on film thickness and microstructural parameters, highlighting their potential for applications in multifunctional devices.

Keywords: Fe doped CuO thin films; n-p type charge transition; Room temperature ferromagnetism