Abstract
In recent years, surface plasmon effects have attracted increasing interests in the development of optical waveguides, biosensors, surface enhanced Raman scattering, and novel photonic devices. Because of its advantages of strong surface plasmon effect, excellent stability, chemical inactivity, and reusability, Au has been extensively used in many applications related to surface plasmon effects. Although there are lots of studies on the surface plasmon effects of Au nanostructures, there are far less works on plain Au films and nanoporous Au films. Therefore, this thesis aims to study the surface plasmon properties of these two types of Au films. For Au films with thicknesses ranging between 1 and 30 nm, a surface resonance peak can be found in the scattering spectrum of a film. The peak wavelength increases when the film thickness increases and the resonance intensity is strongest at the thickness of 10 nm. From SEM and AFM images, this result can be related to the grain size and surface morphology of the films. With the aid of photolithography, Au film patterns with a size of 100×100 □m2 and thicknesses of 10 to 60 nm are prepared. Interesting surface plasmon resonance modes are found at film edges, which will be called edge plasmon resonance modes. Three peaks appear at around 515, 585, and 640 nm in wavelength in a scattering spectrum. The first two peaks increase and the last peak decrease when the film thickness increases. These three modes are argued to result from the non-ideal boundaries due to the shadow effect in metal deposition. Using PMMA for sensitivity test, we can find red-shifts in all these three modes, and the highest value of sensitivity is 122 nm R.I.U.□1. Nanoporous Au films with thicknesses of 10 to 60 nm are prepared by co-deposition of Cu and Au and sequentially and de-alloying. A hole plasmon resonance mode is found in the scattering spectrum of a film. Furthermore, we can find a red-shift when the pore size is increased and a blue-shift when the pore density is raised. Using PMMA and ODT (1-octadecanethiol) for sensitivity test, the changes in peak wavelengths in the scattering spectra are not obvious, and the highest sensitivity is only 20 nm R.I.U. □1.