Anomalously large intermixing in aluminum-transition-metal bilayers

Intermixing has been studied in thin films of the form X/Al and Al/X, where X represents the transition metals in rows 4, 5, and 6 of the periodic table. Samples were grown by dc magnetron sputter deposition at room temperature and investigated using grazing-incidence x-ray reflectometry. Scans of the specular reflectivity have been fitted to determine the total interface width. We deduce the intermixing profile at the interface and separate it from the topographical roughness. Here intermixing has been measured in the great majority of the systems, and we find that there is a wide range in the extent of the intermixing. We bring to the attention of the thin-film community the surprisingly large degree of intermixing at room temperature in many cases. This phenomenon is not predicted by bulk diffusion parameters.