Tailoring cobalt nanostructures via e-beam glancing angle deposition method: Thickness-dependent effects on optical and photocatalytic properties

Cobalt (Co) thin films were deposited onto silicon substrates to the thicknesses of 50 nm, 160 nm, 240 nm, and 360 nm in order to analyze the changes in optical and photocatalytic properties. The morphology of the films was characterized by an increase in column diameter and porosity with increasing film thickness. X-ray diffraction and transmission electron microscopy analyses demonstrated that the deposited samples exhibit a fine-grained structure. The chemical analysis revealed that metallic Co is the predominant phase in the deposited films, with a certain amount of the oxide phase. Optical properties, including the refractive index and extinction coefficient, exhibit variations with thickness, which can be attributed to the changes in the microstructure and porosity. Additionally, the electrical resistivity was found to decrease with thickness, suggesting relationship between film structure and conductivity. Both, optical and electrical properties were influenced by the growth mechanism, with behavior strongly linked to defect concentration and the metallic nature of the Co thin films. Finally, the photocatalytic activity of the cobalt nanostructures demonstrated their capability to degrade methylene blue organic dye under light irradiation, highlighting the potential of Co nanomaterials for environmental remediation applications.