title: Encapsulated annealing: enhancing the plasmon quality factor in lithographically-defined nanostructures.
abstract: Lithography provides the precision to pattern large arrays of metallic nanostructures with varying geometries, enabling systematic studies and discoveries of new phenomena in plasmonics. However, surface plasmon resonances experience more damping in lithographically-defined structures than in chemically-synthesized nanoparticles of comparable geometries. Grain boundaries, surface roughness, substrate effects, and adhesion layers have been reported as causes of plasmon damping, but it is difficult to isolate these effects. Using monochromated electron energy-loss spectroscopy (EELS) and numerical analysis, we demonstrate an experimental technique that allows the study of these effects individually, to significantly reduce the plasmon damping in lithographically-defined structures. We introduce a method of encapsulated annealing that preserves the shape of polycrystalline gold nanostructures, while their grain-boundary density is reduced. We demonstrate enhanced Q-factors in lithographically-defined nanostructures, with intrinsic damping that matches the theoretical Drude damping limit.
authors.affiliation: 1] Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602 [2].
authors.forename: Michel
authors.initials: M
authors.lastname: Bosman
authors.affiliation: 1] Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117583 [2].
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.affiliation: College of Physics and Microelectronics, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha 410082, China.
authors.forename: Huigao
authors.initials: H
authors.lastname: Duan
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543.
authors.forename: Shu Fen
authors.initials: SF
authors.lastname: Tan
authors.affiliation: 1] Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602 [2] Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543 [3] Solar Energy Research Institute of Singapore (SERIS), 7 Engineering Drive 1, National University of Singapore, Singapore 117574, Singapore [4] Graphene Research Centre, National University of Singapore, 2 Science Drive 3, Singapore 117542.
authors.forename: Christian A
authors.initials: CA
authors.lastname: Nijhuis
authors.affiliation: Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117583.
authors.forename: Cheng-Wei
authors.initials: CW
authors.lastname: Qiu
authors.affiliation: 1] Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602 [2] Singapore University of Technology and Design (SUTD), 20 Dover Drive, Singapore 138682.
authors.forename: Joel K W
authors.initials: JK
authors.lastname: Yang