Nano-scale interface modification of the Co/Cu system: metallic surface modifiers in the growth of smooth thin films

Abstract

This review is a collection of twelve original papers concerning growth and interface modification in the Co/Cu system. Most of this research has been carried out in the Laboratory of Surface and Thin Film Physics at the Institute of Nuclear Physics. The Laboratory was created by the author of this review in 1996 in strong collaboration with the Institute of Nuclear Physics Wilhelms-Universität in Münster, Germany and the Institute of Applied Physics Ukrainian Academy of Science in Sumy, Ukraine. The big international team worked under the leadership of Dr Marta Marszałek, initially developing a multicomponent ultrahigh vacuum setup for thin film preparation and analysis, and next accompanying her in studies of the structural, magnetic and magnetotransport properties of Co/Cu multilayers. Systems that exhibit giant magnetoresistance effect have been receiving intensive attentions over recent years since they are possible candidates for applications in ultrahigh-density data storage and magnetoelectronic devices. The focus of this research is the growth of magnetic Co/Cu multilayers modified by using metallic surface modifiers called surfactants. The different approaches have been used. Surfactant metals were introduced once into growth process as a buffer layer or they were deposited sequentially at each interface of Co/Cu multilayers. The growth was performed by molecular beam epitaxy technique which allows to tailor carefully deposition conditions. The results showed that two approaches gave different results. Surfactant buffer layers resulted in loss of layered character of multilayers being a kind of an intermediate cluster-like phase combined with a layered area. Small amount of surfactants introduced at each interface lead to well-ordered structures with small roughness and smoother interfaces than in the case of pure Co/Cu multilayers. Despite of the differences, in both cases the improvement of magnetoresistance value was observed. The atomic scale study of Co growth on Cu(111) surface in the presence of In surfactant demonstrated that surfactant facilitates layerby- layer growth of cobalt on Cu(111). The surfactant effect of indium is connected to a reduction in the cobalt surface diffusion rate (with increased energy barrier) and therefore lowered ratio of Ehrlich- Schwoebel barrier to surface diffusion barrier.