X-ray microdiffraction study of growth modes and crystallographic tilts in oxide films on metal substrates.

Abstract

The crystallographic texture of thin-film coatings plays an essential role in determining such diverse materials properties as wear resistance, recording density in magnetic media and electrical transport in superconductors. Typically, X-ray pole figures provide a macroscopically averaged description of texture, and electron backscattering provides spatially resolved surface measurements. In this study, we have used focused, polychromatic synchrotron X-ray microbeams to penetrate multilayer materials and simultaneously characterize the local structure, orientation and strain tensor of different heteroepitaxial layers with submicrometre resolution. Grain-by-grain microstructural studies of cerium oxide films grown on textured nickel foils reveal two distinct kinetic growth regimes on vicinal surfaces: ledge growth at elevated temperatures and island growth at lower temperatures. In addition, a combinatorial approach reveals that crystallographic tilting associated with these complex interfaces is qualitatively described by a simple geometrical model applicable to brittle films on ductile substrates. The sensitivity of conducting percolation paths to tilt-induced texture improvement is demonstrated.