Role of film–substrate interface in the internal friction of nanocrystalline diamond films

In light of recent measurements which indicate a dominant role in the low-temperature internal friction for interface-layers of diamond films grown on silicon substrates, the internal friction of a series of four nanocrystalline diamond films was measured. The films, all 0.5 μ m thick, had internal friction silimar in magnitude to those reported before, Qf−1≈4×10−6, below roughly 100 K. However, no dependence on interface-layer structure was found, contrary to expectations. The films did exhibit a low-temperature internal friction peak, at 1–2 K, which was also observed in previous films.