Synthesis of unstrained failure-resistant nanocrystalline diamond films

Nanocrystalline diamond films are highly strained materials, in general. This situation precludes from taking advantage of the many superlative properties of diamond that make it suitable for protective and tribological coatings (i.e. chemical inertness, hardness). Unstrained failure-resistant nanocrystalline diamond films were obtained by performing bias-enhanced nucleation in a microwave chemical vapor deposition system followed by nanocrystalline diamond deposition in a hot-filament chemical vapor deposition system. Thermal-shock tests showed that the bias-seeded films return to their initial unstrained state after differentially contracting and expanding, unlike nanocrystalline diamond films deposited on standard abrasion-seeded substrates, which undergo substantial stress changes that indicate the rupture of interfacial bonds. These results are discussed in terms of the nanocomposite interfacial structure induced by bias-seeding that enhances the nanocrystalline diamond film's tolerance to failure.