Roughness-dependent wetting behavior of vapor-deposited metallic thin films

Abstract

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.

Effect of Fe Doping on the Surface Morphology and Supercapacitor Properties of Sr(OH)2 Thin Films: A Fractal Approach

“…The average local surface slope (ρ) is described by the relation ρ = ⟨(▽ z ) 2 ∝ w /ξ a ⟩. The local surface slope is time independent for the roughening process. , For α ∼ 1, this expression reduces to ρ ≈ w / ξ , which has a crucial role for the surface. In this case, ρ is a measure of the competition between smoothing due to the lateral growth and roughening due to the vertical growth. , The calculated values of ρ are given in Table .…”

“…The local surface slope is time independent for the roughening process. 34,35 For α ∼ 1, this expression reduces to ρ ≈ w/ξ, which has a crucial role for the surface. In this case, ρ is a measure of the competition between smoothing due to the lateral growth and roughening due to the vertical growth.…”

“…In this case, ρ is a measure of the competition between smoothing due to the lateral growth and roughening due to the vertical growth. 34,35 The calculated values of ρ are given in Table 1.…”

“…33 Foadi et al studied the roughness-dependent wettability of vapor-deposited metallic thin films. 34,35 Surface morphology plays an essential role in governing the supercapacitive behavior of the material. An enhanced surface area increases the reactivity.…”

“…Wang et al reported a relationship between the fatigue threshold value and fractal dimension . Foadi et al studied the roughness-dependent wettability of vapor-deposited metallic thin films. , …”