Transmission electron microscopy based study of epitaxy in Nb ∕ ( 100 ) Cu bilayer and Cu ∕ Nb ∕ ( 100 ) Cu trilayer nanoscale films

• Published in: Applied physics letters 2005-01, Vol.86 (5), p.051904-051904-3
• Main Authors: Mitlin, D., Schmid, A. K., Radmilovic, V.
• Format: Article
• Language: English
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.1850195

We used transmission electron microscopy to detail the structure of Nb ∕ Cu ( 100 ) thin films and Cu ∕ Nb ∕ Cu ( 100 ) trilayers grown by physical vapor deposition. The two dominant orientation relationships that exist between the Nb and the Cu are the Bain and the Kurdjumov-Sachs (K-S). However, there is an angular spread in these orientations, which is evident in the selected-area diffraction patterns and in the high-resolution transmission electron microscope images. The first several monolayers of Nb maintain a Bain orientation relationship with the Cu substrate. As the overlayer thickness increases, the Nb grains begin to tilt away from the Bain orientation, around the [010] Cu direction, creating a "domino-like" microstructure. This tilting is associated with the presence of dislocations in the Nb, with the projection of their Burgers vector perpendicular to the Nb ∕ Cu interface. The dislocations are located several monolayers offset from the interface. The K-S grains are observed to heterogeneously nucleate near the dislocation cores. Surprisingly, when Cu is deposited to cap the Nb films, the overlayer grows as a single crystal in a Bain orientation with the underlying Nb, essentially ignoring the K-S oriented grains.