Scrutinizing Au nanoparticle arrays with scattering-type scanning near-field optical microscopy

• Main Authors: Tian-You Cheng, 鄭天佑
• Other Authors: Jiun-Haw Lee
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/41981355563684579887

博士 === 國立臺灣大學 === 光電工程學研究所 === 101 === Anomalous optical properties displayed by plasmonic structures are commonly attributed to the enhanced, local field within their corrugations. Though theoretical calculations of such field enhancements abound, experimental observations are relatively few, because only few optical microscopic techniques have enough spatial resolution. The scattering-type scanning near-field optical microscope (s-SNOM)—operating based on the electromagnetic interaction induced by a nanotip—transforms local field characteristics to far-field radiation for detection. The lateral resolution and vertical resolution of s-SNOM are 9 nm and 10 nm, respectively. The local optical characteristics of gold nanoparticle array with a gap of 10 nm between adjacent particles are resolved by s-SNOM with use of sharpened silicon tips. Specifically, the local, enhanced field—“hot spot”—is observed at the gap region and the local field direction is extracted as well. These two distinctive near-field traits are interpreted with a proposed dipole-coupling model. The findings corroborate that s-SNOM is a powerful analytical instrument to reveal optical characteristics in sub-10 nm scale and would be expectantly beneficial to the development of optical applications based on two-dimensional sub-wavelength plasmonic structures and their epistemological understanding.