Structure of sputtered Co–Se thin films prepared for an application in catalysis

Co–Se thin films prepared by magnetron sputtering have shown significant activity for the oxygen reduction reaction. One sample, after sectioning by ultramicrotomy, was studied by high-resolution scanning transmission electron microscopy (HRSTEM) and scanning Auger microscopy (SAM), and X-ray diffraction (XRD) was used for characterizing further samples. These thin films were shown to have Co–Se nanocrystals embedded into Se-rich matrices. The TEM and XRD results were consistent with the nanocrystallites being non-stoichiometric with structures related to those of monoclinic Co1−xSe (x=0.125–0.25).