Mechanical Properties of Boron-Doped CVD Diamond Films

For this study, single-crystal and polycrystalline diamond films with different boron contents were synthesized in a hot-filament chemical vapor deposition (CVD) apparatus to evaluate the mechanical properties of these films. Boron was added to the diamond by introducing B(CH3)3 :trimethyl boron diluted to 1000 ppm with hydrogen into the diamond-synthesis atmosphere. The synthesized diamond film's crystallinity was evaluated using Raman spectroscopy. The Hertz fracture strength was measured using a diamond-ball indenter. Furthermore, the wear resistance of the film was evaluated using a wear testing machine. The results indicate that the crystallinity of the single-crystal diamond film increased concomitantly with increasing boron content. Furthermore, the Hertz fracture strength increased by 20% with the addition of boron. Results clarified that the wear volume of polycrystalline diamond film decreased to approximately one-third its usual value by the addition of boron. These results show that the mechanical properties of boron-doped diamond films can be improved considerably by adding an appropriate amount of boron.