Investigation of the wetting layer in a metallic fluid KxKCl1-x solution by spectroscopic ellipsometry

Spectroscopic ellipsometry in the energy range 0.8 eV less than or equal to h nu less than or equal to 2.7 eV was employed at temperatures up to 730 d egrees C to study the dielectric function epsilon = epsilon(1) + i epsilon( 2) of a wetting layer in a metal rich K0.95KCl0.05 solution. The epsilon(2) -spectra measured at temperatures above the wetting transition at coexisten ce (T = 590 degrees C) and near coexistence (T = 660 degrees C) are similar to the spectrum of a KCl-rich bulk phase which shows a characteristic F-ce ntre absorption band in the near infrared region. At a temperature off coex istence and above the prewetting transition (T = 730 degrees C) the dispers ion of the epsilon(2)-spectrum in the near infrared is reduced compared to the lower temperatures. These findings are consistent with previous experim ents which indicate that a salt rich wetting phase intrudes between the met al rich phase and a sapphire substrate above the wetting temperature T-w si milar to 500 degrees C at coexistence. (C) 1999 Published by Elsevier Scien ce B.V. All rights reserved.