Wettability of HF-CVD diamond films

Wettability of HF-CVD diamond films grown in different conditions has been investigated. Wettability depends on surface tension: solids with high surface tension, as diamond, should be hydrophilic, while solids with low surface tension should be hydrophobic. In spite of these arguments, natural diamond exhibits a moderate hydrophobicity [J. Cell. Inter. Sci. 130 (1999) 35], depending on surface termination (hydrogen or oxygen terminated). In this work we find that CVD diamond films show wettability behaviours ranging from a small, up to clear hydrophobicity, probably according to surface carbon termination functionalities. Wettability does not seem to be influenced by characteristics as film structural morphology or growth orientation direction, which were analysed by SEM, while it seems dependent on surface reconstruction, as detected by Raman and XPS analysis. Moreover, in contrast with natural diamond [J. Cell. Inter. Sci. 130 (1999) 35] we found an enhancement to water wettability when CVD diamond films were treated in a hot filament activated hydrogen atmosphere. We argue that this effect may be due to the hydrogen etching of reconstructed surface layers with lower surface tension