How Is Oxygen Incorporated into Oxides? A Comprehensive Kinetic Study of a Simple Solid‐State Reaction with SrTiO₃ as a Model Material

Abstract

The kinetics of stoichiometry change of an oxide--a prototype of a simple solid-state reaction and a process of substantial technological relevance--is studied and analyzed in great detail. Oxygen incorporation into strontium titanate was chosen as a model process. The complete reaction can be phenomenologically and mechanistically understood beginning with the surface reaction and ending with the transport in the perovskite. Key elements are a detailed knowledge of the defect chemistry of the perovskite as well as the application of a variety of experimental and theoretical tools, many of them evolving from this study. The importance of the reaction and transport steps for (electro)chemical applications is emphasized.

Unraveling the enhanced Oxygen Vacancy Formation in Complex Oxides during Annealing and Growth

“…5 one then expects a stronger reduction of the STO crystal when exposed to this atmosphere. Additionally it is conceivable that the ionization can influence the kinetics of the redox-reaction at the sample surface in a way that the removal of oxygen from the sample gets favorable38. In conclusion the cold cathode and mass spectrometer are primarily responsible for the unexpected reduction of STO at relatively high oxygen pressures; probably due to their working principle, which is based on ionization.…”

Oxygen partial pressure dependence of surface space charge formation in donor-doped SrTiO3

“…15,20 The lower temperature limit at which the surface defect chemistry of the oxygen and strontium sublattices needs to be considered is already well investigated for acceptor-doped SrTiO 3 . However, it is much more complex for donor-doped SrTiO 3 , due to long equilibration times, secondary phase formation, 22 and the stronger influence of cations as electronic charge compensating species. 15 Complementing defect chemical considerations, at lower temperatures, the presence of charged adsorbates might influence n-SrTiO 3 surfaces in oxidizing conditions.…”

“…(La,Sr)MnO 3 δ 25 ), with finite concentrations up to 1000 K and thus might be considered on SrTiO 3 , too. 22,54 Hence, the adsorption of charged oxygen molecules might be possible even at higher temperatures. From the observed shift of the Fermi energy, it is possible to determine the maximum negative surface charge to ∼10 14 e/cm 2 which corresponds to a possible surface coverage of ∼8% and ∼16% for V Sr and chemisorbed charged oxygen molecules, respectively.…”

Thermodynamic stability and growth kinetics of epitaxial SrTiO3on silicon

“…Nor does an SiO 2 interface layer form after the sample has been removed from the growth chamber and kept at ambient conditions for months or even years. By this we mean that the experimentally measured rates of oxygen incorporation 29,30 and diffusion [30][31][32] in bulk SrTiO 3 under ambient conditions suggest that the system should reach equilibrium in a reasonable time period. What prevents the system from evolving to its equilibrium state and thus enables the growth of epitaxial SrTiO 3 /Si?…”