Thick Self-Ordered Nanoporous Ta2O5 Films with Long-Range Lateral Order

In this work we report the anodic formation of highly ordered nanoporous Ta 2 O 5 layers that exhibit a self-ordered alignment of pores uniformly over the anodized surface. These layers are grown by anodization of tantalum in a nonaqueous electrolyte consisting of an optimized glycerol/ethylene glycol mixture with the addition of NH 4 F. To reach an optimized nanoporous structure, several factors [fluoride concentration and content of supporting electrolyte (NH 4 ) 2 SO 4 ] need to be controlled. Once optimized, the nanopore diameter can be adjusted using the applied voltage in the range of 7-18 nm, and layers with a thickness of more than 10 μm can be grown. As a result, a pore aspect ratio of > 1000 can be reached.

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