Surface-plasmon resonance as a sensitive optical probe of metal-film properties

Abstract

The resonance excitation of surface plasmons, detected by the scattered-light method, is used in a number of experiments on Ag, Au, and Cu films. These include (i) the determination of optical constants, (ii) the use of a multilayered structure allowing sequential excitation of plasmons on both surfaces of a film, (iii) the study of interference between bulk- and surface-plasmon scattered light, and (iv) the demonstration of surface anisotropy on films grown with the metal vapor beam striking the substrate at an oblique angle. The optical-constant measurements, which were done on the substrate interface, agree with data on bulk samples prepared and measured in vacuum and with film data by Dujardin and Thèye, but they disagree with film data by Schulz and by Johnson and Christy. In samples grown on 77-K substrates a strong increase in bulk scattering is observed which interferes with the roughness-coupled plasmon signal producing a dispersive line shape rather than the usual Lorentzian.