Optical studies on individual Au nanodisks

Abstract

ABSTRACT

Plasmon arises from the oscillation of electrons in conduction band with the existence of external electromagnetic field. Plasmonics has attracted a worldwide interest for its various applications, such as surface-enhanced Raman/fluorescence spectroscopy[1], lithography fabrication[2], biological and chemical sensors[3] and so on.

Since the first observation of single photon luminescence from metal in 1969 by A. Mooradian, many efforts have been paid to explore the underlying physical mechanism. After enhancement of photoluminescence intensity in rough film or nanoparticles was observed, there are many debates on the role of plasmon in the photoluminescence mechanism, from enhancing the local electric field in photoluminescence process to plasmon radiative decay. As the development of the nanoscale fabrication techniques, arbitrary shape and size of nanoparticles can be obtained for investigating the photoluminescence mechanism on metal nanostructures[4].

The Localized surface plasmon depend on the size and shape of the gold nanostructures, so varied size and shape of the gold nanostructures were investigated to illuminate more details on the mechanism of plasmon modulated metal photoluminescence. During the optical measurements, both dark-field scattering and photoluminescence will be applied on the samples.

The polarization dependence of the photoluminescence on the gold nanostructures is also an important approach to study the role of the plasmon in PL process. Symmetric circle gold nanodisks with different size were fabricated for investigation. The incomplete depolarization we observed here is attributed to the high electric field distribution regions where non-equilibrium electrons intend to excite plasmon.[5]

In summary, this thesis investigates detailed mechanism on the optical properties of individual Au nanodisks. The fabrication of the gold nanostructures by Electron Beam Lithography provides a precise and versatile way to approach the control of the optical properties of individual Au nanostructures.