Thin Metal Films and Surface Plasmons By: Joel Rovner and Will Bagienski.

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Thin Metal Films and Surface Plasmons By: Joel Rovner and Will Bagienski

Our Goal Was: Create thin films of metals Compare thickness measurements made by different methods: deposition monitor, resistance, and surface plasmon resonance.

Thickness Measurement Deposition monitor: Uses a vibrating quartz crystal Sensitive to added mass on crystal Gives rate and total thickness Resistance: resistivity of silver p = 1.59 x 10^-8 ohm meters Area of film: about 2.5 x 2.5 cm Surface Plasmons: Laser table, measure reflected intensities, Look for resonance

Surface Plasmons Surface Plasmons are oscillations of the free electron gas at the surface of a metal. In this lab we tried to detect them by shining a laser on the films. If we could detect them we could have used our results to estimate the films thickness. The dispersion relation for surface plasmons is ω=ck x sqrt(1+(1/1-(ω p /ω) 2 )). Glass Metal Air Surface Plasmon

Experimental Apparatus The apparatus consisted of a digital light intensity meter, a red laser, an angle table, a power supply, and the thin film. The angle of incidence of the laser was held constant and the detector arm was turned until the reflected light was detected. Some of the problems that developed were that it was very difficult to make small changes to the angle of incidence and detect it without accidentally changing it. Laser

Results: Indium 1: forgot to open shutter (oops) Indium 2: meter thickness: 500 angstroms, but didn’t conduct, couldn’t use other methods. Silver 1: 750 angstroms on meter, about 400 angstroms by resistance, couldn’t find SP resonance. Silver 2: 333 angstroms on meter, about 150 by resistance, still couldn’t find SP resonance  Made nice mirrors though!!!

What went wrong? Each time we evaporated, vacuum got a little worse, despite resealing. Too much air in chamber, some reaction? Uniformity of the film? Tarnished? Laser table and measurement procedure? Resonance too small to see? Something else? The true thickness remains a mystery…

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