title: Nanogap effects on near- and far-field plasmonic behaviors of metallic nanoparticle dimers.
abstract: In the field of plasmonics, the nanogap effect is often related to one aspect like the near-field enhancement at a single excitation wavelength or the far-field resonance shift. In this study, taking full advantage of finite element method (FEM) calculations, we present a comprehensive and quantitative analysis of the nanogap effect on the plasmonic behaviors of metallic nanoparticle dimers. Firstly, near-field spectroscopy is proposed in order to extract the near-field resonance wavelengths. Focusing on the bonding dipole mode, it is found that the near-field enhancement factors exhibit a weak power-law dependence on the gap size, while the near-field resonance shift decays nearly exponentially as the gap size increases, with a lower decay length than that for the far-field resonance shift. The spectral deviation between these two shifts is suggested to be taken into account for spectroscopy applications of plasmonic devices, although it may be negligible for dimer structures with rather small gaps.
authors.affiliation: State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, P. R. China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, P. R. China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, P. R. China.
authors.forename: Mengjing
authors.initials: M
authors.lastname: Hou
authors.affiliation: State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, P. R. China.
authors.forename: Lingwei
authors.initials: L
authors.lastname: Ma
authors.affiliation: Key Laboratory of Advanced Materials (MOE), School of Materials Science and Engineering, Tsinghua University, Beijing 100084, P. R. China. zjzhang@tsinghua.edu.cn.
authors.forename: Zhengjun
authors.initials: Z
authors.lastname: Zhang