Detailed Structural Analysis of Epitaxial MBE-Grown Fe/Cr Superlattices by X-Ray Diffraction and Transmission-Electron Spectroscopy

We have performed a detailed quantitative structural analysis of epitaxial [Fe(3 nm)/Cr(1.2 nm)] 20 superlattices by low- and high-angle x-ray diffraction, and energy-filtered transmission electron microscopy on cross-section samples. The interface roughness was changed systematically by varying the substrate temperature (150–250°C) maintaining all other growth parameters fixed. Direct imaging of the interfaces allows examining the roughness of the individual interfaces and its evolution with thickness. A statistical analysis of the local interface width for the individual layers supplies the roughness static and dynamic exponents. High-temperature samples (250°C) show roughness decreasing with thickness as a result of surface-diffusion-dominated growth. Low-temperature samples (150°C) show anomalous non-self-affine roughness characterized by a time-dependent local interface width.