Structural studies of Co/Cr multilayered thin films

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Abstract
The structural properties of Co/Cr multilayered structures (ML’s) with bilayer thickness varying from 14 to 400 Å and total thickness of about 3000 Å have been studied. These ML’s were prepared by e-beam vapor deposition of the elemental metals onto temperature-controlled oxidized single-crystal Si substrates. Several sets of multilayers were fabricated in order to investigate various types of effects. It was determined that the multilayer crystallites grow as bcc Cr layers in the [110] direction and hcp Co layers in the [10.1] direction. Crystallites of hcp [00.2] Co and/or [110] Cr and [10.0] Co also occur systematically in some of the ML. The detailed structures of the ML’s (the individual layer, bilayer, and interface thicknesses as well as the length of the various crystallites) were determined by modeling the multilayers as having interfaces with a linear variation in composition and fitting the measured large-angle x-ray-scattering spectra to calculated spectra. This analysis indicates that the bilayers of the ML crystallites have asymmetric interfaces as would result from the rate of diffusion or penetration of the Co into Cr being much larger than that of Cr into Co. There is no evidence for any bcc Co. The growth of the ML can be described by three empirical rules. The interface thicknesses of a few ML’s having complete alignment were also determined from saturation-magnetization measurements; the two methods gave good agreement.