High resolution x-ray characterization of Co films on Al2O3

Publisher Website
Google Scholar
Abstract
We have studied the structural properties of Molecular Beam Epitaxy grown thin Co films on α‐sapphire (112̄0) substrates by high resolution x‐ray scattering measurements in the thickness range of 100 Å to 5000 Å. The electron density profile perpendicular to the film plane was determined by x‐ray specular reflectivity measurements. The profile contains information about the total metal film thickness, an oxide layer on top of the film and about the surface and interface roughness. The total metal film thickness was compared with the number of coherently scattering atomic planes by taking radial scans through Bragg peaks parallel to the growth direction. Samples up to 400 Å total thickness (out‐of‐plane mosaicity 0.02○) show very strong Laue‐oscillations about the Co (0002)/(111) Bragg peak. Above a total thickness of 400 Å the oscillations vanish due to a loss in structural coherence. The combination of specular reflectivity and Bragg scans presents a powerful means to analyze the structural coherence of thin films.