Fabrication of Nanoporous Ceramic Thin Films: De-alloying and Self-organized Template Formation Onamorphous Substrates

Sol-gel-derived metal oxide ceramic thin films deposited onto amorphous iron-rich substrates were found to form self-organized nanoporous structures dependent upon the extent to which the substrate is de-alloyed, a function of the substrate alloy composition, acid concentration of the sol, and film drying conditions. Field emission scanning electron microscopy, transmission electron microscopy, and x-ray energy dispersive analysis were used to investigate details of the porous structure formation. Our studies showed the more electrochemically active elements in the amorphous substrate are de-alloyed by the sol in high-humidity environments, whereupon the liberated elements form oxides replicating the de-alloyed substrate matrix resulting in a three dimensional porous network structure.

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