Coherency strains and growth of artificially modulated CuNi thin films

The structure of CuNi thin films containing short-wavelength compositional and strain modulations is studied by electron microscopy (RHEED, CTEM, and XTEM). Extended defects are investigated, predominantly, the double-positioning twinning and high-angle grains. A mode of columnar growth is observed while the direct observation of modulation fringes reveals sets of inclined interfaces and surfaces with certain crystallographic symmetry. The role of the coherency strains in such growth of metastable materials is examined within the theory of continuum elasticity. The possible significance of these structural characteristics on various anisotropic physical properties is also discussed.