Toward nκd spectroscopy: Analytic solution of the three-phase model of polarimetry in the thin-film limit

We find an analytic solution of the three-phase (substrate/overlayer/ ambient) model of polarimetry in the thin-film limit, which allows overlayer thicknesses d and refractive indices ñ =n+iκ to be determined from measured changes Δρ ρ of the complex reflectance ratio ρ and Δ Rp Rp or Δ Rs Rs of the p - or s -polarized reflectances Rp or Rs, from a quadratic equation without the need for potentially unstable numerical methods. We also find a transformation of the data that extends the range of accuracy by up to an order of magnitude without introducing additional mathematical complications. The results are illustrated by the application to a layer of physisorbed H2 O on oxidized GaAs, and show that the wavelength-by-wavelength spectroscopy of adsorbed monolayers is now within range of existing polarimetric technology. © 2006 American Institute of Physics.