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Comparative surface studies of oxygen passivated FeCo nanoparticles and thin films



We present results on the comparative studies of the surfaces of oxygen passivated FeCo nanoparticles (NPs) and thin films prepared by inert gas condensation and pulse laser deposition, respectively. Morphology and structure of the NPs and thin films are investigated by transmission electron microscopy (TEM) and X-ray diffraction. Due to the larger surface area, thicker oxide over-layer is observed for particles in comparison with thin films. X-ray photoelectron spectroscopy (XPS) spectra strongly depended on the morphology and oxide over layer thicknesses for nanostructures. This leads to observation of clearly different background and is explained in term of different cationic distribution in the overlayer, thicknesses, and morphology (enhanced surface area) of the nanostructures. TEM analyses showed an oxide over-layer on the NP of approximately 2.6 nm, which is consistent with the theoretical model based on electron attenuation lengths. However, in the case of thin films a much thinner oxide over-layer of about 1.3 nm was observed. As expected, XPS spectra of oxygen passivated particles show oxide peaks with weak metal peaks compared to oxygen passivated thin films which show significantly high zero-valent metal peaks.