Mechanical properties of boron nitride films prepared by plasma-enhanced chemical vapor deposition

Two kinds of boron nitride thin films, cubic boron nitride film with a layered structure, and turbostratic boron nitride film with a c-axis parallel to the substrate surface, were prepared by inductively coupled plasma-enhanced chemical vapor deposition. Nanoindentation tests revealed that the hardness and elastic modulus of cubic boron nitride films increased with cubic phase content and approached approximately 50 and 250 GPa, respectively, for the case of 96% cubic phase, while those of turbostratic boron nitride films were load and loading rate dependent and as low as 1.5 and 30 GPa, respectively. Moreover, the hysteretic recovery of turbostratic boron nitride after indentation was confirmed, and approximately 50% of the energy dissipated during indentation was found to be released within 1 min.