Structures and adhesion of hcp thin film coating interfaces on a single-crystal bcc substrate by PVD: Ti/Mo and Zr/Mo

Polycrystalline hcp Ti and Zr thin films were developed on single-crystal bcc-Mo (110) substrate using PVD method. XRD analysis suggests the preferred facet relation of (0001)hcp//(110)bcc. Sandwich supercell models were then constructed to evaluate the interface energy, adhesion strength and bonding nature from the first principles. The Burgers and Pitsch-Schrader orientation relation (OR) were predicted as the most energy-favored for the PVD Ti and Zr thin film interfaces on the Mo (110), respectively. Interface adhesion was predicted to be fairly strong for both interfaces. The d-d orbital interaction between Ti/Zr and Mo is found closely associated with the spatial redistribution of Bader valence charges. The resulting new bonds across the interfaces are rather delocalized, showing a mixed covalent and weak ionic bond character. These results strongly suggest that single-crystal Mo (110) is a promising substrate for developing high quality hcp Ti or Zr thin films through PVD.