Aluminium-alumina interface morphology and thermodynamics from dewetting experiments Original Research Article

This work presents the morphology of micron-sized metallic drops (Al) equilibrated on ceramic substrates (sapphire), with emphasis on the interfacial region. The samples were made by controlled dewetting of a thin Al film on the basal surface of sapphire substrates, at temperatures above the melting point of Al. Morphological inspections showed that evaporation of the sapphire substrate atoms, which diffuse at the interface, has an important role in the evolution of the Al-sapphire interface morphology. The absolute value of the sapphire basal surface energy was extracted (1279 ± 78 mJ/m2 at 900 °C). The values of the thermodynamic parameters determined from the interface morphology agree well with those from experiments made under identical conditions but using millimetre-sized drops. This confirms the validity of Young’s equation for large sessile drops in systems undergoing limited morphological changes (ridging) at the interface.