Effect of metallic seed layers on the properties of nanocrystalline diamond films

Abstract

Three metallic films (Mo, Ti and W) were sputtered on Si substrates and ultrasonically seeded in diamond powder suspension. Nanocrystalline diamond (NCD) films were deposited using a dc arc plasma jet CVD system on the seeded metallic layers and, for comparison, a seeded Si without any metallic layer. The effect of metallic seed layers on the nucleation, microstructure, composition and mechanical properties of NCD films was investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and nanoindentation. We found that the metallic seed layers were transformed into metallic carbide or/and metallic silicide during the deposition of NCD films at high temperature. Adding metallic seed layers had no obvious effect on the bonding structure of the NCD films but significantly improved their surface roughness and mechanical properties. The NCD film deposited on W seed layer displays the lowest root-mean-square roughness of 19nm while that on Ti seed layer has the highest compactness, hardness and elastic modulus.