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We studied the wetting behavior of silver and copper thin films versus their kinetic roughening upon deposition at room temperature on glass substrates. Time-dependent height-height correlation functions were extracted from atomic force microscopy images, and they demonstrated a nonstationary growth front of the film roughness associated with a temporal evolution of the local surface slope. As a result, we tried to correlate the roughness statistical properties such as the root-mean-square (rms) roughness σ , the correlation length ξ , and the local surface slope (ρ ≈ σ /ξ ) with the wetting behavior of the films' surfaces. The contact angle behavior was also studied by analyzing the variation of the energy of the system with water penetrating into the surface cavities, and the associated Laplace pressure induced by the local surface curvature. Hence, it was demonstrated that the wetting transition from a metastable Cassie-Baxter state to a Wenzel state as well as the penetration of a droplet into the surface crevices occur at the smaller local surface slopes for the higher surface energy material.

Wetting properties of the 304 stainless steel indicate a hydrophilic nature. In this study, two methods including Cu 2 O thin film coating and chemical etching process have been applied on stainless steel substrates in order to fabricate hydrophobic surfaces. Cu 2 O films were synthesized using spray pyrolysis method at different deposition temperatures and different 2-propanol concentrations. X-ray diffraction (XRD) patterns obtained for the surfaces prepared at different temperatures showed different copper oxide phases well. In addition to XRD results for the samples prepared at different 2-propanol concentrations, the value of optical band gap for these surfaces calculated from UV-Vis spectra confirmed formation of Cu 2 O structure. Statistical parameters of the surfaces were calculated using atomic force microscopy (AFM) data including rms roughness σ, roughness exponent α and correlation length x. A similar behaviour was found between water contact angle and local surface slope r s x » a ( )of thin films. However, in the etching process of steel substrates, the effect of substrate roughness in obtaining water contact angle as high as ≈115°on the Cu 2 O surface was well established. The morphological properties of these latter surfaces were also studied by scanning electron microscopy (SEM). Generally, knowing statistical information of surface as well as chemical manipulations can be helpful to reach optimal conditions for synthesis of a hydrophobic surface.

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