Mechanical properties and quality of diamond films b

Microwave plasma-enhanced chemical vapor deposition was used to grow diamond films on Ti
6Al4V alloy using various gas phase precursors. The results of four types of experiments with
different gas mixtures are compared: ~1! 2% CH4 in H2; ~2! initial saturation of 5% CH4 in H2
followed by 2% CH4 in H2; ~3! a CO-rich mixture with a CO:H2 ratio of 8; and ~4! a hybrid mixture
of 2% CH4 in H2 followed by a CO:H2 ratio of 8. The substrate temperature during deposition with
CH4 /H2 mixtures was between 715 and 810 °C, and was between 550 and 600 °C when CO/H2
mixtures were used. Optical emission spectroscopy was used to monitor the excited gas-phase
species in the plasma. The films were characterized by micro-Raman spectroscopy, glancing-angle
x-ray diffraction, and nanoindentation. The films grown with the type ~1! mixture often exhibited
good quality with high hardness ~70 GPa! but suffered from poor adhesion to the substrate. The
films grown with the type ~2! mixture were of slightly lower quality and hardness ~58 GPa! but
exhibited better adhesion. The films produced from the type ~3! mixture were adhered, but exhibited
very low growth rates and low hardness ~18 GPa!. Finally, the films produced from the hybrid type
~4! mixture were of poor quality and suffered from poor adhesion to the substrate. The differences
in interfacial phases and mechanical properties for each film are discussed and the usefulness of
each gas mixture for the diamond growth is evaluated. 微波等离子体增强化学气相沉积系统(MPECVD)