A resistometric study of Nb/Ta single-crystal superlattices

Abstract

We report on resistometric measurements of precisely deposited films of single-crystal Nb/Ta superlattices. These superlattices have been uhv sputter deposited onto a buffer layer of epitaxial NbTa alloy which was itself deposited onto a variety of different sapphire substrate orientations. Using lithographic patterning, comparisons of the resistance ratio and resistivity of small strips were made along the substrates across which a known variation in composition has occurred. The superlattices, which contain near-integral numbers of monolayers, show some additional variation of resistance ratio along the length of substrate in excess of that expected for a fixed interfacial mixing. A preliminary model to illustrate this effect is developed which takes account of intermixing at the interfaces. Anodisation spectroscopy results are presented which provide information about the atomic registry and interfacial roughness of superlattices.