A model system, involving 190nm of Al deposited onto 140nm layer of W on a MgO(00l) substrate, was studied. The W layer was <00l>-oriented and was rotated by 45º with respect to the MgO substrate in order to minimize misfit. The remaining strain was accommodated by dislocations; as revealed by transmission electron microscopy. By using high-resolution X-ray diffraction measurements, the out-of-plane lattice parameter was deduced to be 0.3175nm, while the in-plane parameter was 0.3153nm. That is, the W film supported a strain which resulted in a tetragonal distortion of the lattice. The X-ray diffraction pole figures showed that the Al had 4-fold symmetry, and 2 predominant orientations, <016> and <3 9 11>, which were twinned with multiple placements on the epitaxial W layer. The driving force for the tilted <001> and <011> orientations of Al on W was strain-minimization via lattice-matching. The results showed that (001)Al deposition onto W under ambient conditions was difficult to achieve, and this implied that electromigration difficulties were inherent.

Texture of Al Thin Films Deposited by Magnetron Sputtering onto Epitaxial W(001). L.D.Madsen, E.B.Svedberg, D.B.Bergstrom, I.Petrov, J.E.Greene: Journal of Applied Physics, 2000, 87[1], 168-71