OES time-resolved characterization of the deposition of multilayered Cr/CrN coatings

Multilayered structures with nanometric periods and nanocomposite materials are probably the most promising alternatives to improve the properties of conventional coatings used for mechanical applications. Most of the multilayered structures referred to in the literature present mechanical properties that surpass those of their individual materials: increase of hardness, elastic limit and toughness, and reduction of internal stresses. Optical emission spectroscopy (OES) is used in this work to characterize the transient gas composition regime during the deposition of multilayered structures by rf magnetron sputtering in a continuous process, with multilayer periods down to the nanometric scale. A single cathode with a metallic target (Cr) is used, and the alternate deposition of two materials is achieved by periodically alternating the working gas composition. A good correlation is found between time response values assessed by OES and relative thickness ratio values on Cr/CrN multilayers by LA-XRD and transmission electron microscopy (TEM). Time-resolved OES plasma measurements are a useful tool to monitor in situ the formation of well-defined multilayer structures in a continuous process, with multilayer periods down to a few nanometers.