Interface structure and overgrowth orientation for niobium and molybdenum films on sapphire substrates II. R-plane substrates

Abstract

We show that when niobium and molybdenum films are sputter deposited on R-plane sapphire substrates, {001} growth is misoriented, and the angle of misorientation is different for the two metals, being 2.6° for niobium and 3.8° for molybdenum. By characterizing the interface dislocation array in both systems, we show that the misorientations can consistently be interpreted in relation to the differing non-misfit-relieving Burgers vectors components of the geometrically necessary misfit dislocation arrays present for the two systems. The way in which this indicates that the metal overgrowth immediately adjacent to the sapphire is perfectly oriented is discussed in relation to the interface-dominated mode of growth implied.