Dependence of interfacial adhesion of Co-P film on its microstructure

The interfacial adhesion between electroplated Co-P films with various microstructures and substrate was thoroughly investigated by the nanoscratch method and transmission electron microscopy. The Co-P films with various P contents exhibited a completely amorphous structure, a nanocrystalline structure or a mixed structure. The experimental data show that the interfacial adhesion of the Co-P films strongly depends on their microstructure and the nanocrystalline film has stronger interfacial adhesion than the amorphous film. The intermetallic Co-Cu phase that forms at the interface between the nanocrystalline Co-P film and the substrate causes the increase of the adhesion strength. In addition, the first-principles calculation shows that the intense exchange coupling between Co(3d(7)4s(2)) electrons and Cu(3d(10)4s(1)) electrons results in the formation of the Co-Cu bond at the interface between the nanocrystalline Co-P film and the substrate and hence increases the interfacial adhesion strength. (C) 2012 Elsevier B.V. All rights reserved.