Chemisorption of water and carbon dioxide on nanostructured BaTiO3–SrTiO3(001) surfaces.

The interaction of water and carbon dioxide with nanostructured epitaxial (Ba,Sr)TiO₃(001) thin film and bulk single crystal SrTiO₃(001) surfaces was studied using x-ray photoemission spectroscopy (XPS), thermal desorption spectroscopy (TDS), and density functional theory (DFT). On both surfaces, XPS and TDS indicate D₂O and CO₂ chemisorb at room temperature with broad thermal desorption peaks (423–723 K) and a peak desorption temperature near 573 K. A comparison of thermal desorption Redhead activation energies to adsorption energies calculated using DFT indicates that defect surface sites are important for the observed strong adsorbate-surface reactivity. Numerical calculations of the competetive adsorption/desorption equilibria for H₂O and CO₂ on SrTiO₃(001) surfaces show that for typical atmospheric concentrations of 0.038% carbon dioxide and 0.247% water vapor the surfaces are covered to a large extent with both adsorbates. The high desorption temperature indicates that these adsorbates have the potential to impact measurements of the electronic structure of BaTiO₃–SrTiO₃(001) surfaces exposed to air, or prepared in high vacuum deposition systems, as well as the electrical properties of thin film ATiO₃-based devices. [ABSTRACT FROM AUTHOR]