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

Area of Science:

• Materials Science
• Surface Science
• Thin Film Deposition

Background:

• Understanding the relationship between thin film surface morphology and wetting properties is crucial for various applications.
• Kinetic roughening during film growth influences surface characteristics and subsequent interactions with liquids.

Purpose of the Study:

• To investigate the correlation between the kinetic roughening of silver and copper thin films and their wetting behavior.
• To analyze how surface roughness parameters (rms roughness, correlation length, local slope) affect wetting transitions.

Main Methods:

• Atomic Force Microscopy (AFM) was used to capture surface topography.
• Time-dependent height-height correlation functions were analyzed to characterize film roughness evolution.
• Contact angle measurements and energy variation analysis were performed to study wetting phenomena.

Main Results:

• Film roughness exhibited a nonstationary growth front with evolving local surface slopes.
• A correlation was established between roughness statistics (σ, ξ, ρ) and wetting behavior.
• Wetting transitions (Cassie-Baxter to Wenzel) and droplet penetration occurred at smaller local surface slopes for higher surface energy materials.

Conclusions:

• The study demonstrates a direct link between kinetic roughening dynamics and the macroscopic wetting properties of thin films.
• Local surface slope is a critical parameter governing wetting transitions and liquid penetration into surface cavities.
• Surface energy plays a key role in determining the conditions under which wetting transitions occur.