title: Eutectic combinations as a pathway to the formation of substrate-based Au-Ge heterodimers and hollowed au nanocrescents with tunable optical properties.
abstract: Pairs of immiscible elements with deep eutectics are used to synthesize periodic arrays of heterodimers and hollowed metal nanocrescents. In the devised route, substrate-immobilized Au or Ag nanostructures act as heterogeneous nucleation sites for Ge adatoms. At elevated temperatures the adatoms collect in sufficient quantities to transform each site into a AuGe liquid alloy which, upon cooling, phase separates into elemental components sharing a common interface. The so-formed Au-Ge and Ag-Ge heterodimers exhibit a complex morphology characterized by a noble metal nanocrescent which partially encapsulates one end of the Ge domain. Through the use of a selective etch the Ge component is removed, leaving behind a periodic array of hollow noble metal nanocrescents on the surface of the substrate. Optical characterization of both the heterodimers and nanocrescents indicates that the presence of Ge gives rise to a relative blue-shift in the localized surface plasmon peak, a result that is in stark contrast to the red-shifts typically observed when plasmonic nanostructures are in contact with a dielectric medium. Simulations are used to both rationalize the observed shift and show the potential for deriving unexpected behaviors when semishell-like noble metal structures are in contact with high permittivity dielectric mediums.
authors.affiliation: College of Engineering, Temple University, Philadelphia, Pennsylvania, 19122, USA.
authors.forename: Aarthi
authors.initials: A
authors.lastname: Sundar
authors.forename: Pouyan
authors.initials: P
authors.lastname: Farzinpour
authors.forename: Kyle D
authors.initials: KD
authors.lastname: Gilroy
authors.forename: Teng
authors.initials: T
authors.lastname: Tan
authors.forename: Robert A
authors.initials: RA
authors.lastname: Hughes
authors.forename: Svetlana
authors.initials: S
authors.lastname: Neretina
keywords: heterodimers; hybrid; nanocrescents; plasmon; semishell