Structural, morphological, and optical properties of fe-doped SrCo2O4 thin films prepared by sol-gel dip-coating

This study investigates the synthesis of novel Fe-doped SrCo 2 O 4 nanostructured thin films through sol–gel dip-coating method. The films have been thoroughly analyzed using XRD, SEM, AFM, IR and UV-Vis. X-ray diffraction confirmed that all films crystallize in a single-phase cubic spinel structure (space group Fd-3m). Fe incorporation at the Co sites induced a slight lattice expansion, increasing the unit-cell volume from 528.38 to 528.84 Å 3 , while the average crystallite size decreased from 25.17 to 18.70 nm, accompanied by an increase in microstrain and dislocation density. A scanning electron microscope revealed a progressive transformation from a porous surface to a denser and more compact morphology with increasing Fe content, whereas atomic force microscopy showed an island-like surface structure with the average roughness reaching a maximum of 65.74 nm at 3 at% Fe before decreasing to 38.08 nm at 6 at% Fe. The FTIR spectra of SrCo 2 O 4 thin films exhibited the characteristic metal-oxygen stretching bands at approximately 572 cm − 1 and 669 cm − 1 , confirming the spinel phase structure of the nanoparticles without detectable hydroxyl or carboxyl functional groups. The optical properties were discussed via UV-Visible diffuse reflectance spectroscopy technique using Kubelka-Munk function, showed a fundamental bandgap in the energy range of 2.90 eV 3.42 eV, with an additional sub-band corresponding to energies varying between 1.05 and 1.57 eV for all samples. These findings demonstrate that Fe doping was found to effectively tailors the crystal structure, surface morphology, and optical response of SrCo 2 O 4 thin films, highlighting their potential for advanced optoelectronic, supercapacitors, and energy-storage applications.