Direct imaging of the near field and dynamics of surface plasmon resonance on gold nanostructures using photoemission electron microscopy

Abstract

Localized surface plasmon resonance (LSPR) can be supported by metallic nanoparticles and engineered nanostructures. An understanding of the spatially resolved near-field properties and dynamics of LSPR is important, but remains experimentally challenging. We report experimental studies toward this aim using photoemission electron microscopy (PEEM) with high spatial resolution of sub-10 nm. Various engineered gold nanostructure arrays (such as rods, nanodisk-like particles and dimers) are investigated via PEEM using near-infrared (NIR) femtosecond laser pulses as the excitation source. When the LSPR wavelengths overlap the spectrum of the femtosecond pulses, the LSPR is efficiently excited and promotes multiphoton photoemission, which is correlated with the local intensity of the metallic nanoparticles in the near field. Thus, the local field distribution of the LSPR on different Au nanostructures can be directly explored and discussed using the PEEM images. In addition, the dynamics of the LSPR is studied by combining interferometric time-resolved pump-probe technique and PEEM. Detailed information on the oscillation and dephasing of the LSPR field can be obtained. The results identify PEEM as a powerful tool for accessing the near-field mapping and dynamic properties of plasmonic nanostructures. Keywords: femtosecond laser; local field enhancement; near-field imaging; photoemission electron microscopy; surface plasmon resonance INTRODUCTION Because of the rapid development of nanofabrication techniques, metallic nanostructures that can exhibit localized surface plasmon resonance (LSPR) can be fabricated using several methods. The resonance frequency and amplitude of LSPR on metallic nanostructures are known to depend on the metal materials, shapes, and surrounding media. [1][2][3][4] In addition, the LSPR can confine optical fields in nanoscale space, leading to the so-called local field enhancement effect. These unique properties promote the application of LSPR in many fields, such as surface-enhanced Raman scattering, 5-8 sensing, 1,9,10 plasmonassisted photochemical reactions 4,11,12 and photocurrent generation. [13][14][15] To further understand the LSPR mechanism and to optimize the design of the plasmonic nanostructures for most applications, the near-field properties of the LSPR fields (especially the near-field distribution of the plasmonic nanostructures) must be determined. To date, investigations of the optical properties of LSPR have largely relied on far-field spectroscopic techniques or numerical simulations. Several experimental approaches have been utilized to visualize the near field, including scanning photoionization microscopy, 16,17 scanning near-field optical microscopy, 18-21 nonlinear luminescence or fluorescent microscopy, 22,23 nonlinear photopolymerization 24,25 and near-field ablation of a substrate. [26][27][28][29] However, these approaches have

Insight into plasmonic hot-electron transfer and plasmon molecular drive: new dimensions in energy conversion and nanofabrication

“…Sun et al 51 successfully applied this technique to the direct imaging of the near-field and dynamics of SPR on gold NSs. Various kinds of gold NS arrays (such as rods, nanodisks and their dimers) fabricated by electron-beam lithography were investigated via excitation with femtosecond NIR laser beams.…”

Nanowire-supported plasmonic waveguide for remote excitation of surface-enhanced Raman scattering

“…The former could overcome the traditional diffraction limit in dielectric optics and be the key approach to overcoming the bottleneck of the miniaturization of nanophotonic devices and large-scale on-chip integrated circuits for next-generation information technology. [5][6][7][8][9][10][11] The extremely enhanced EM field caused by the latter has great application values in various fields, such as surface-enhanced spectrum, [12][13][14][15] surface plasmon resonance sensors, [16][17][18][19] ultra transmission, 20,21 plasmonic trapping, 22,23 plasmonic-enhanced emission, 24,25 quantum communication, 26,27 super-resolution microscopy, 28 cloaking, 29 photothermal cancer therapy, 30,31 steam generation, 30,32,33 holography, 34 photovoltaics [35][36][37] and water splitting. [38][39][40] One of the most promising applications of SPPs, especially localized SPPs, is surface-enhanced Raman scattering (SERS), which has been studied both theoretically and experimentally for many decades.…”

Failure mechanism analysis and process improvement on time-dependent dielectric breakdown of Cu/ultra-low-k dielectric based on complementary Raman and FTIR spectroscopy study

“…It is well known that the complementary application of Raman and Fourier transform infrared (FTIR) vibrational spectroscopy is one of the most common characterization tools and methodology for low-k and ultra-low-k material analyses and characterization. [10][11][12][13][14][15][16][17][18][19][20] In present work, we will describe the experiments and the setup to capture the dielectric bonding damage during the reliability test and an physical model based the experimental results was proposed on the Ta ions migration model and the line-edge-roughness (LER) model. Details on the two models are discussed in later sections.…”