NbZr multilayers. II. Extended x-ray-absorption fine-structure study

Extended x-ray-absorption fine-structure (EXAFS) measurements have been used to study the atomic-scale structure of a series of ten multilayer films of NbZr with layer-spacing periods $\Lambda$ ranging from 4 to 200 Å. It is found that the Zr layers have a gradual hcp-to-bcc transformation as the layer-spacing period decreases, being predominately hcp for $\Lambda \gg 50$ Å and predominately bcc for $\Lambda \ll 50$ Å. It is also shown that the layers are not sharp but rather that there is significant interdiffusion. Assuming that one multilayer period contains two interdiffusive layers at the boundaries between the two constituent films, we estimate that diffusion lengths of Nb into Zr and Zr into Nb at the interlayer are about 15 Å for sputtered NbZr multilayers.