DETERMINATION OF THE X-RAY-SCATTERING LINESHAPE FROM A NB THIN-FILM USING SYNCHROTRON-RADIATION

Detailed measurements of the x-ray scattering from a 400 Angstrom thin film of Nb grown on sapphire have been performed using synchrotron ra diation From a bending magnet. Bragg reflections from Nb planes perpen dicular to the surface normal have a two-component lineshape: a sharp, essentially resolution-limited peak, superimposed on a diffuse Lorent zian-squared component. In contrast, Bragg peaks with a finite wavevec tor transfer in the plane of the film display the broad component only . These measurements indicate that the lattice mismatch between the me tallic overlayer and substrate is relieved by the formation of domains randomly rotated in the plane of the film.