Anisotropic surroundings effects on photo absorption of partially embedded Au nanospheroids in silica glass substrate

Xuan Meng,Ruixuan Yu,Junya Ishioka,Tamaki Shibayama,Seiichi Watanabe

doi:10.1063/1.4908010

Abstract

The influence of a directly adjacent or an anisotropic surrounding medium alters the plasmonic properties of a nanoparticle because it provides a mechanism for symmetry breaking of the scattering. Given the success of ion irradiation induced embedment of rigid metallic nanospheroids into amorphous substrate, it is possible to examine the effect of the silica glass substrate on the plasmonic properties of these embedded nanospheroids. In this work presented here, discrete dipole approximation (DDA) calculations for the Au nanospheroids’ optical properties were performed based on 3–dimensional (3D) configuration extracted from planar SEM micrographs and cross–sectional TEM micrographs of the Au nanospheroids partially embedded in the silica glass, and the well–matched simulations with respect to the experimental measurements could demonstrate the dielectric constant at the near surface of silica glass decreased after Ar–ion irradiation.

Highlights

Nanostructured noble metals exhibit remarkable optical properties due to the excitation of localized surface plasmons (LSPs) by incident light, which has stimulated considerable applications in diverse fields such as surface enhanced Raman spectroscopy (SERS),[1,2,3] solar cell,[4,5,6,7] and biosensors.[8]
The pioneering works focused on the optical response of Ag nanospheres embedded in silica glass was studied by discrete dipole approximation (DDA) method, and the authors concluded that the local surface plasmon resonance (LSPR) shifted linearly towards the longer wavelength with the surface area of the embedded parts.[9]
In this work presented here, DDA simulations for the Au nanospheroids’ optical properties are performed based on 3D configuration extracted from planar SEM micrographs and cross–sectional transmission electron microscope (TEM) micrographs, and we show that the well–matched simulation with respect to the experimental observations is possible to elucidate the dielectric constant at the near surface of the silica glass decreased under Ar–ion irradiation

Summary

INTRODUCTION

Nanostructured noble metals exhibit remarkable optical properties due to the excitation of localized surface plasmons (LSPs) by incident light, which has stimulated considerable applications in diverse fields such as surface enhanced Raman spectroscopy (SERS),[1,2,3] solar cell,[4,5,6,7] and biosensors.[8]. The pioneering works focused on the optical response of Ag nanospheres embedded in silica glass was studied by DDA method, and the authors concluded that the LSPR shifted linearly towards the longer wavelength (red–shift) with the surface area of the embedded parts.[9]. In this work presented here, DDA simulations for the Au nanospheroids’ optical properties are performed based on 3D configuration extracted from planar SEM micrographs and cross–sectional TEM micrographs, and we show that the well–matched simulation with respect to the experimental observations is possible to elucidate the dielectric constant at the near surface of the silica glass decreased under Ar–ion irradiation

EXPERIMENTAL PROCEDURE AND RESULTS

DDA CALCULATION OF PHOTO ABSORPTION COEFFICIENT

CONCLUSIONS