Interface properties in sequence permutated Fe–B–Ag multilayers

Abstract

Fe-B-Ag multilayers have been prepared in two different sequences of the layers in order to reveal distinctness of "top" and "bottom" interfaces of each element in relation to the other two elements. Transmission electron microscopy analysis showed a much larger interface roughness for the Fe/ B/Ag ͑i.e., Fe at bottom, Ag on top of B͒ than for the B/Fe/Ag sequence, which is mainly due to the different growth processes of Ag. For both sequence Fe and B layers of 2 nm thickness are continuous and solid state amorphization-similar to that observed in Fe/B multilayers-takes place during sample growth. Mössbauer spectroscopy measurements indicate that the amorphous interface has a broad bimodal concentration distribution for both layer sequence, but intermixing is larger at the Fe/B than at the B/Fe interface.

Interfaces in sequence permutated multilayers

“…The layer permutation, however, influenced the sample morphology to a large extent, as it was revealed by transmission electron microscopy investigations [2]. Large interface roughness and waviness of the layers was observed when Ag was grown on top of the B layer, but B was found to grow on Ag smoothly.…”

“…This way the accuracy of the interface analysis is greatly enhanced, since the experimental uncertainties of the layer thickness measurement can be excluded for the selected layers. Analysis of the results obtained by MS for sequence permutated sample pairs had shown [2] that the composition of the amorphous Fe/B and B/Fe interfaces are different, chemical mixing is larger at the interface where B is on top of the Fe layer.…”

“…The application of the above method is limited by possible mixing and diffusion between the 57 Fe and the natural Fe layers. A new approach, sequence permutation of three building block multilayers [2], was suggested recently. In order to distinguish the bottom and top interfaces of the Fe layer a third element is interleaved, and the multilayers composed of three different elemental layers are deposited by sequence permutation in two different forms, as it is illustrated in figure 1.…”

“…In order to distinguish the bottom and top interfaces of the Fe layer a third element is interleaved, and the multilayers composed of three different elemental layers are deposited by sequence permutation in two different forms, as it is illustrated in figure 1. The Fe/B multilayer system was chosen [2] to be studied this way because a significant mixing of the elements accompanied by solid state amorphization occurs at the interfaces [3] already during the sample deposition and Ag was interleaved since it does not mix with either of the two elements: both Fe-Ag and B-Ag are non-mixing element pairs. The sequence permutated sample pairs can be prepared simultaneously in such a way that two of the building blocks (e.g.…”

Chemical mixing at “Al on Fe” and “Fe on Al” interfaces

“…Deviation from this expectation indicates that the distribution of the elements is different across the top and the bottom interface, which is often termed shortly as interface asymmetry. The non-mixing Ag layer modifies the hyperfine parameters of only 2-3 Fe monolayers (MLs), 17 which can be taken into account. One should remark that some mixing of Ag and Fe can take place during the non-equilibrium processes of thin film growth, 18 …”