Interface structure and overgrowth orientation for niobium and molybdenum films on sapphire substrates I. A-plane substrates

Abstract

We report a comparison of the epitaxies of niobium and molybdenum sputter deposited on A-plane sapphire substrates. In the niobium case, the cores of the dislocation arrays associated with the interfacial misfit relief are localized in the metallic overgrowth, some 7 to 9 Å away from the sapphire, and the dislocations adopt standard body-centred cubic-type Burgers vectors. For molybdenum, the dislocation array lies very close to the compositional interface. The way this difference in interface structure leads to different epitaxial behaviours for the two systems is discussed.