title: Sub-micron free-standing metal slabs with dielectric nano-voids of arbitrary shapes embedded beneath atomically-flat surface.
abstract: Thin metal slabs with plasmonic nano-voids buried within the skin depth (< 25 nm) of surface plasmon polaritons have been of theoretical as well as technical interests for many years due to its unique optical properties such as sharp absorbance dips and anti-crossing plasmonic dispersion characteristics. Unfortunately, such interesting plasmonic properties have not been experimentally reproduced, especially in the UV-Vis regime, owing to the involuntary surface roughness occurred in systems fabricated using conventional techniques. Here, we describe a versatile cryogenic-stripping approach for encapsulating a monolayer of nano-voids of virtually any arbitrary shapes underneath an atomically-smooth (δ < 0.55 nm) surface of a free-standing metal slab. By artificially varying the topography of the capping metal surface from ultra-smooth to moderately-rough, we show structural symmetricity in a nano-void-metal system can render the overall plasmonic responses becoming profoundly influenced by the surface smoothness. The current fabrication technique is thus of primary importance to the preparation of any kind of smooth nano-void-passivated metal slabs.
authors.affiliation: Department of Physics, National University of Singapore, Science Drive 3, 117542 Singapore.
authors.forename: Kiang Wei
authors.initials: KW
authors.lastname: Kho
authors.forename: Zexiang
authors.initials: Z
authors.lastname: Shen
authors.forename: Malini
authors.initials: M
authors.lastname: Olivo