title: Metal double layers with sub-10 nm channels.
abstract: Double-layer plasmonic nanostructures are fabricated by depositing metal at normal incidence onto various resist masks, forming an antenna layer on top of the resist post and a hole layer on the substrate. Antenna plasmon resonances are found to couple to the hole layer, inducing image charges which enhance the near-field for small layer spacings. For continued evaporation above the resist height, a sub-10 nm gap channel develops due to a self-aligned process and a minimal undercut of the resist sidewall. For such double layers with nanogap channels, the average surface-enhanced Raman scattering intensity is improved by a factor in excess of 60 in comparison to a single-layer antenna with the same dimensions. The proposed design principle is compatible with low-cost fabrication, straightforward to implement, and applicable over large areas. Moreover, it can be applied for any particular antenna shape to improve the signals in surface-enhanced spectroscopy applications.
authors.affiliation: Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut , 5232 Villigen-PSI, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Siegfried
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Yasin
authors.initials: Y
authors.lastname: Ekinci
authors.forename: Olivier J F
authors.initials: OJ
authors.lastname: Martin
authors.forename: Hans
authors.initials: H
authors.lastname: Sigg