Directed fabrication of radially stacked multifunctional oxide heterostructures using soft electron-beam lithography

A versatile patterning approach based on electron-beam lithography (eBL) and solution deposition, termed soft-eBL, has been developed to fabricate radially stacked heterostructures of multifunctional oxides from their sol precursors. Well-defined nanorings of lead zirconate titanate (PZT) are fabricated on a variety of substrates such as noble metals (e.g., Au), semiconductors (e.g., Si), and oxide single crystals (e.g., SrTiO₃), which were previously functionalized with appropriate self-assembled monolayers (SAMs). The undercut in the double-layer eBL resist and substrate functionalization with the SAM treatment play a vital role in the formation of the ring structures. The nanorings are then used as building block "containers" and ring-reservoirs are filled with a second sol (e.g., CoFe₂O₄) to form radially stacked composite ceramic hetero-structures. The approach presented here does not require either feature alignment to realize heterostructures or the etching of ceramics, and is amenable to a variety of radially stacked composite heterostructures.