Effect of Boron Doping Concentration on the Wettability and Surface Free Energy of Polycrystalline Boron-Doped Diamond Film

The wettability and surface free energy of diamonds are crucial for their applications. In this study, polycrystalline boron-doped diamond (PBDD) films with different boron doping concentrations were prepared, and the effect of the boron doping concentration on the wettability and surface free energy (SFE) of the film was investigated. The SFEs of the PBDD films were investigated by employing the surface tension component approach and the equation-of-state approach. The investigation suggested that the alternative formulation of Berthelot's rule, the Lifshitz-van der Waals/acid-base (van Oss) approach, and the Owens-Wendt-Kaelble approach were suitable for estimating the SFEs of PBDD films, whereas the Fowkes approach, Berthelot's (geometric mean) combining rule, and Antonow's rule could not provide reliable results. Results showed that the SFEs of PBDD films increased with increasing boron doping concentration, and the SFEs were 43.26-49.66 mJ/m(2) (Owens-Wendt-Kaelble approach), 42.89-52.26 mJ/m(2) (Lifshitz-van der Waals/acid-base), and 44.38-48.73 mJ/m(2) (alternative formulation of Berthelot's rule). This study also provides a reference for the application of empirical and physics-based semi-empirical approaches to SFE estimation.