The innovation engine for new materials

Redox-Kinetics of Donor-Doped SrTiO3 - Fundamentals and Applications of a Model Material

Seminar Group: 


Professor Rainer Waser


Forschungszentrum Jülich and RWTH Aachen University
Aachen, Germany


Tuesday, July 26, 2016 - 2:00pm


Elings 1601


Prof. Susanne Stemmer

Perovskite-type oxides exhibit a plethora of fascinating electronic material properties covering an exceptionally wide range of phenomena in solid state and surface physics. The prototypical perovskite SrTiO3 (STO), its isostructural cousin BaTiO3 (BTO), and their solid solutions belong to the most widely studied oxides because of their diverse functionalities.

The electrical properties of donor-doped SrTiO3 (n-STO) are profoundly affected by an oxidation induced metal-insulator transition (MIT). In this seminar, we present dynamical numerical simulations to examine the high-temperature MIT of n-STO over a large range of time and length scales. The simulations are based on the Nernst–Planck equations, the continuity equations, and the Poisson equation, in combination with surface lattice disorder equilibria as time-dependent boundary conditions. The simulations reveal that n-STO, upon oxidation, develops a kinetic space charge region (SCR) in the near-surface region. The surface concentrations of the variously mobile defects (electrons, Sr vacancies, and O vacancies) are found to vary over time and to differ considerably from the values of the new equilibrium. The simulation results will be compared to experimental diffusion and conduction data. 

n-STO, n-BTO, and their solid solutions are commercially used as ceramics for thermistors and grain-boundary layer capacitors for many decades. Furthermore, n-STO is explored for functionalities such as thermoelectricity, memristive switching, and photoelectrolysis. We discuss implications of our findings for the electrical conductivity of n-STO crystals used as substrates for epitaxial oxide thin films, of n-STO thin films and interfaces, as well as of polycrystalline n-STO with various functionalities.