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

• The effect of three different metallic seed layers on the properties of the NCD films was discussed.
• The metallic layers were transformed into metallic carbide and/or metallic silicide.
• The bonding structure of the NCD films is almost not affected.
• The surface roughness and the mechanical properties of NCD films were significantly improved.
• The smoothest NCD film was obtained on W layer and the film on Ti shows the best mechanical properties.

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 19 nm while that on Ti seed layer has the highest compactness, hardness and elastic modulus.