Process controlled nanostructure and superhydrophobicity of thin films prepared ablating titanium in mixed argon/nitrogen atmospheres

Thin films were synthesized using pulsed laser ablation of a titanium target in a controlled atmosphere of argon (Ar) and nitrogen (N2). By varying the Ar/N2 ratio at constant total pressure of 40 Pa, we explored the effect of the gas composition on the surface morphology and superhydrophobic properties of the films. In films deposited in pure gas (Ar or N2) arrays of nearly spherical nanoparticles grow, whereas in films grown in mixed Ar/N2 atmospheres complex cauliflower-like structures develop. These morphological differences, influenced by the Ar/N2 ratio, resulted in varying sizes and densities of the surface features, with contact angles exceeding 150 degrees, corresponding to superhydrophobic behavior. Numerical analyses, including Fourier transform and multifractal analysis, confirmed the presence of dual-scale hierarchical structures responsible for the superhydrophobicity. Our results demonstrate that by adjusting the Ar/N2 ratio it is possible to tune the surface properties of thin films, offering potential applications in coatings and sensors requiring specific wetting characteristics.