ISS and AES studies of the initial oxidation of Dy, Tb and their silicides

Samples of Tb and Dy as well as their silicides were oxidized in high vacuu m under controlled conditions for oxygen exposures ranging up to 50 L(1 L = 1 x 10(-6) Torr.s). The oxides were studied by Auger electron spectroscopy (AES) and ion scattering spectroscopy (ISS). Distinct low energy Auger pea k shape changes occurred during the oxidation of the metals as well as duri ng the oxidation of the metal silicides. These peak shape changes are very similar for Tb and Dy as expected due to the similarities in chemical prope rties of the lanthanide elements. When the silicides were exposed to oxygen , both the metal and the Si were oxidized. in both cases the oxide layers w ere enriched by the metal. The depletion of the Dy just below the surface s uggested oxygen induced surface segregation of Dy. A model is proposed in w hich the low energy region of the ISS spectra were used to determine the Si peak height. (C) 1999 Elsevier Science S.A. All rights reserved.