Studying the Influence of Dealloying on Combinatorial W-Fe Thin Films for Development of Porous Nanostructures

A combinatorial material science approach coupled with a chemical dealloying technique is presented to fabricate highly porous nanostructured thin films. Using the magnetron sputter co-deposition process, precursor W_1-xFe_x(0.22 < x <0.52 at. %) thin film materials libraries were fabricated. In order to synthesize highly porous nanostructures and to investigate the influence of selective dissolution of Fe from the film, the materials libraries were dealloyed in aqueous HNO₃ solution for various dealloying durations. The dealloying process resulted in formation of a variety of nanostructures with various compositions and large effective surface areas. Extended dealloying duration led to drastically reduced Fe concentration and formation of WO₃ nanoflake-like structures. Highest WO₃ nanoflake-like structure density was observed on W-rich side, while nanopetal-like agglomerates are noticed on Fe-rich side on the materials library. After t_d = 1440 min, the overall film thickness increased between 70-100 % in comparison to the as-deposited film thickness. This combinatorial high-throughput approach enables screening of a large quantity of compositions having different microstructures to accelerate the search for desired properties and thus promises a useful method for the development of WO₃ nanostructures for future applications.