Fabrication of narrow-gap nanostructures using electron-beam induced deposition etch masks

Abstract

We present an optimized procedure to create narrow-gap nanostructures using electron-beam induced deposition etch masks. Incorporation of a Cr sacrificial layer in between Au metal layer and EBID mask improves the etch mask lithography in terms of dimension control and surface flatness. EBID mask writing is performed with a single-pass strategy varying the dose during writing. This patterning strategy allows us to create relatively thick EBID masks with steep, narrow gaps. An argon sputter etch is used to transfer the mask into the underlying material where the low etching rate of sacrificial layer compared to the EBID mask improves transfer of the mask pattern into the metal nanostructure. A Cr wet etch step is then used to remove sacrificial layer and EBID mask material. We show fabrication of Au dimer nanostructures with gap spacing well below 10nm, down to about 5nm, on Si substrates as well as ITO-coated glass. This method may enable the fabrication of nanostructures with small gap spacing and high degree of material purity and flatness on arbitrarily shaped surfaces.