Interaction Between Liquid Silver and Graphene-Coated SiC Substrate

Wettability between liquid Ag and graphene-coated SiC single crystal has been investigated by dispensed drop method at T = 970 °C under vacuum accompanied with subsecond recording of the drop/substrate images (100 frames per second) by high-speed high-resolution CCD camera. Non-contact heating method coupled with capillary purification of the Ag drop procedure has been applied. Scanning electron microscopy combined with EDS analysis and scanning probe microscopy combined with Raman spectroscopy techniques has been utilized for microstructure and surface characterization of samples before and after high-temperature wetting tests. Immediately after its detachment from the capillary, the Ag drop showed non-wetting behavior (θ > 90°) forming a high contact angle of θ = 114°. Surface characterization of the drop surface after wettability tests evidenced the presence of graphene and Si transferred from the substrate to the top of Ag drop. These findings suggest chemical interaction phenomena occurring at the interface. Locally, an intimate contact between liquid Ag and SiC substrate was allowed by the appearance of discontinuities in the graphene layer basically produced by thermomechanical stress. Local dissolution of carbon into liquid Ag and its reorganization (by segregation, nucleation and growth) as secondary graphene layer at the Ag surface was also observed.