A microscopic study of strongly plasmonic Au and Ag island thin films
Abstract
Thin Au and Ag evaporated films (∼5 nm) are known to form island-like growth, which exhibit a strong plasmonic response under visible illumination. In this work, evaporated thin films are imaged with high resolution transmission electron microscopy, to reveal the structure of the semicontinuous metal island film with sub-nm resolution. The electric field distributions and the absorption spectra of these semicontinuous island film geometries are then simulated numerically using the finite difference time domain method and compared with the experimentally measured absorption spectra. We find surface enhanced Raman scattering (SERS) enhancement factors as high as 108 in the regions of small gaps (≤2 nm), which dominate the electromagnetic response of these films. The small gap enhancement is further substantiated by a statistical analysis of the electric field intensity as a function of the nanogap size. Areal SERS enhancement factors of 4.2 × 104 are obtained for these films. These plasmonic films can also enhance the performance of photocatalytic and photovoltaic phenomena, through near-field coupling. For TiO2 photocatalysis, we calculate enhancement factors of 16 and 19 for Au and Ag, respectively. We study the effect of annealing on these films, which results in a large reduction in electric field strength due to increased nanoparticle spacing.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jan 15, 2013
- Source ID
- 10.1063/1.4775784
Entities
People
- I-kai Hsu
- Jesse Theiss
- Prathamesh Pavaskar
- Stephen B Cronin
- Wei Hsuan Hung
Organizations
- Feng Chia University
- Office of Naval Research
- University of Southern California