AVS 51st International Symposium
    Thin Films Friday Sessions
       Session TF-FrM

Paper TF-FrM5
Comparative Ellipsometric Study of Liquid Helium Thin Films on Au, Cs, HOPG and Rb Substrates

Friday, November 19, 2004, 9:40 am, Room 303C

Session: In-Situ/Ex-Situ & Real-Time Monitoring
Presenter: T. McMillan, University California Irvine
Authors: T. McMillan, University California Irvine
P. Taborek, University California Irvine
J.E. Rutledge, University California Irvine
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We have developed a modulated null ellipsometer with sub-monolayer resolution to measure adsorbed liquid helium thin films at temperatures from 1.3 to 4.3 K. Measuring helium films pushes the limits of cryogenic ellipsometry due to helium's extremely small index of refraction. We have performed isotherms on substrates with a range of substrate potentials: Au is a representative strong substrate while Rb is an intermediate and Cs a weak substrate. These measurements will determine how the binding energy affects the superfluid transition. The ellipsometer allows us to explore effects that cannot be discerned solely from quartz crystal microbalance measurements, which are only sensitive to the normal fluid fraction of the film.