Deposition of PdAu thin films sectioned by sub-15-nm gaps on silicon using direct nanotransfer printing

We have demonstrated direct nanoscale transfer printing of PdAu lines from a hard mold onto a hard substrate at room-temperature without employing any flexible buffer layers or organic adhesion promoters or release agent layers. The molds used in these experiments were GaAs/AlGaAs sandwich structures fabricated by molecular-beam epitaxy that we cleaved and selectively etched afterwards in order to generate 3D grating structures with nanometer resolution on their edges. We fabricated positive multi-line molds with different aspect ratios, linewidths between 15 nm and 100 nm, and spacings between lines ranging from 9 nm to 70 nm. PdAu was evaporated onto the mold surface, and a titanium layer was deposited on top of the PdAu layer. By pressing the mold against a Si/SiO₂ substrate the Ti/PdAu sandwich structure was directly transferred onto the SiO₂ surface. The experiments revealed that direct hard-on-hard transfer of nanoscale structures from a mold onto a substrate can be used to fabricate PdAu gaps with widths of down to 9 nm.