Surface Plasmon Resonance on
Aluminum, Silver and Gold Thin Films
Todd Fallesen '04

Abstract:

    A surface plasmon is a charge density wave that occurs at an interface between a thin film and another medium. Surface plasmons occur whenever energy is incident upon a thin film The plasmon wave can be excited at the interface between a thin metal film and air or other non-metal medium with a positive dielectric sign. The wave can be thought of as having a section inside the thin film and a section outside of the film in the air/metal interface, much like an ocean wave has part of the wave unseen inside the ocean, while another part of the wave is seen in the ocean/horizon interface. Under normal circumstances, a laser light source incident upon a thin film is reflected or scattered, and there would be an insignificant surface plasmon wave, which would absorb very little of the incident energy.

    Surface plasmon resonance occurs when the energy from incident light is of just the right frequency and angle of incidence to couple its energy with the surface plasmon, so that no light is reflected from a normally reflective surface. Thickness of a thin film can be determined through surface plasmon resonance due to the fact that as the thickness of the thin film increases, less of the surface plasmon is in the air/metal interface and more of it is contained within the metal itself. We can use the characteristic peak and shape of the resonance curve to characterize different thin film thicknesses of different materials.

   For more information, contact Dr. Catherine Jahncke:

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