Abstract
This article overviews the formation of ultrananocrystalline diamond (UNCD) by pulsed laser deposition (PLD) and coaxial arc plasma deposition (CAPD), each of which is a kind of physical vapor deposition (PVD). The UNCD formation by these methods need not the pre-treatment of substrates wherein diamond nuclei are seeded using diamond powder, which is a distinctive difference from that by CVD. From the observation of plasma process by optical emission spectroscopy and the structural evaluation of films for the preparation conditions, we have found the followings: 1) a supersaturated condition comprising highly energetic C^+ ions should have an important role in the nucleation of UNCD grains, 2) initial growth might be stabilize and facilitated by the hydrogen termination of surface dangling bonds, 3) grain is enlarged by boron-incorporation, which is consistent with the prediction of a defect-induced diamond growth model.
