Structure and properties of strained compositionally modulated CuNi and PdNi films

Abstract

Thin films of CuNi and PdNi, containing one-dimensional artificial fluctuations in composition and strain, were prepared by vapour deposition. The periodicity of the modulations varied between three and 20 atomic planes. Reflection high energy electron diffraction was used to study the structure of the surface layers. Transmission electron microscopy (in both planar and cross-sectional geometries) was used to study the epitaxy, the interfaces and the structure of these systems. An interesting growth mode in columnar grains, together with embedded twinning, was observed to be the main type of defect. By means of the trace of the modulation-fringe sequences, the interplay of kinetics and the coherency strain thermodynamics may be studied in order to establish mechanisms of growth and to provide improvements in the preparation methodologies. These structural observations are discussed in conjunction with the anisotropy of various properties such as the optical and magnetic properties.