A Combined Photoelectron Spectroscopy and ab Initio Study of the Adsorbate System O₂/PbTe(001) and the Oxide Layer Growth Kinetics

Abstract

The adsorption of molecular oxygen on PbTe(001) surfaces has been investigated using synchrotron radiation induced photoelectron spectroscopy (BESSY II, Berlin). The behavior of adsorbate system O 2 /PbTe(001) was also modeled in complementary DFT-B3LYP studies using a large-cluster approach. For several possible adsorption structures, the adsorption enthalpies, the changes of the effective charges, and the core-level shifts induced by adsorption were calculated. For the energetically most favorable adsorption structures, the calculated chemical shifts are in good agreement with the experimental observations. Oxidation was observed at exposures above ∼10 5 L of O 2 . In total, three steps of oxidation were observed. The first step of the reaction is associated with the formation of Te−O−Pb bonds resulting in Te 0 states. The subsequent second step is characterized by a Te 0 →Te 4+ transformation with three O atoms attaching to each surface Te atom. As a result, −TeO 3 2− species are formed. The third step is associated with the growth of the planar layer of PbTeO 3 . In the range of exposures from 10 11 to 10 15 L, the kinetics of this layer growth can be described with the time-logarithmic law. The oxide growth rate does not depend on the presence of water vapor.