Quantitative and analytical high-resolution transmission electron microscopy study of epitaxial cobalt/copper GMR multilayers

Co/Cu multilayers were grown on Nb layers by sputter deposition as part of an effort to develop a system for producing epitaxial multilayer (ML) devices for perpendicular to plane, giant magnetoresistance measurements (CPP-GMR). Epitaxial MLs and a polycrystalline ML were analyzed using conventional, analytical and high-resolution transmission electron microscopy. The Nb base layer observed was a single defect-dense crystal on the sapphire substrate. Apparently amorphous interfaces and non-equilibrium lattice structures were seen in one epitaxial ML. This sample also showed a overall Cu mass deficit. MLs In the other epitaxial specimens were broken into “island-like” regions associated with Cu seed-layer discontinuity. These epitaxial MLs had strata showing a crystal defect density like the Nb base and Co/Cu interlayer contrast. The polycrystalline sample was small grained and textured in the [111] growth direction. Co/Cu interlayer contrast in the polycrystalline ML and the epitaxial island MLs arises from stacking changes in Co.