Plasma afterglow-assisted oxidation of iron–copper bilayers

• Iron–copper bilayers are deposited by magnetron sputtering
• Bilayers are oxidized by plasma afterglow at atmospheric pressure
• Caterpillar-like patterns covered by CuO and Fe2O3 nanostructures are formed
• Copper comes up through cracks or Fe2O3 layer made permeable by tensile stress
• Localizing nanowires is achievable by creating crack patterns before oxidation.

Iron layers with variable thicknesses, deposited onto copper thin films, are oxidized by a plasma afterglow at atmospheric pressure. Such a bilayer arrangement enables the growth of caterpillar-like patterns covered by CuO and Fe2O3 nanostructures. Two main mechanisms are at stake: either copper comes up to the surface through cracks or boundaries between the columns of the coating, or it diffuses through parts of the Fe2O3 layer made permeable by tensile stress. Structures grown by the former mechanisms are characterized by a central channel, whereas those grown by the latter exhibit a plane interface above which stands an equiaxed grain heap. This result was used to localize the growth of nanowires in cracks formed priory to the afterglow-assisted treatment. By resorting to XPS microscopy experiments carried out with the scanning photoelectron microscope at the ESCAMicroscopy beamline of the Elettra synchrotron facility in Trieste, we could gain access to the surface composition of a single isolated pattern.

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