Analysing the surface morphology of annealed FTO/ZnS bilayer films: stereometric, fractal, and wettability approaches

Abstract

The surface micromorphology and roughening of the thermal evaporation-coated FTO/ZnS bilayer thin films annealed at 300, 400, 500, and $$550\,^\circ{\text{C}}$$ 550 ∘ C for 1 h have been studied. AFM images of the prepared samples were analysed by the MountainsMap software, and the effects of the annealing temperature on the surface texture of the FTO/ZnS thin film’s surface were investigated. Stereometric and advanced fractal analyses showed that the sample annealed at $$500\,^\circ{\text{C}}$$ 500 ∘ C exhibited greater surface roughness and greater skewness and kurtosis. This film also has the most isotropic surface and exhibits the highest degree of heterogeneity. Also, despite the decrease in surface roughness with increasing temperature from 500 to $$550 \,^\circ{\text{C}}$$ 550 ∘ C , the fractal dimension tends to increase. The static water contact angle measurements indicate that the film annealed at $$500 \,^\circ{\text{C}}$$ 500 ∘ C exhibits higher hydrophobicity, which can be attributed to its greater topographic roughness. Our research indicates that the surface morphology of FTO/ZnS bilayer thin films is influenced by the annealing temperature. Changing factors such as roughness, fractality, and wettability parameters to help improve surface performance make the FTO/ZnS bilayer suitable for application in electronic and solar systems.