Charge-Carrier Enrichment at BaZrO3/SrTiO3 Interfaces

Heterogeneous doping through nanostructuring has been demonstrated to greatly enhance the transport and mass storage properties of halides and Li-ion conductors by decoupling of charge-compensating species. In this study, we explore the potential of heterogeneous doping of ionically conducting oxides through first-principles and thermodynamic calculations of a model system consisting of acceptor-doped SrTiO3 and BaZrO3. We show that the two dominating defects, v(o)(center dot center dot) and OHo center dot, are thermodynamically favored in BaZrO3 compared to SrTiO3 by 0.64 and 0.56 eV, respectively, in turn leading to an electrostatic potential barrier as large as 0.64 V (relative to BaZrO3) at 800 K. v(o)(center dot center dot), OHo center dot and electron holes as such accumulate on the BaZrO3 side of the interface, leading to a charge-depletion layer in SrTiO3 which thus acts as a heterogeneous acceptor for BaZrO3. These interface effects may drastically enhance the charge-carrier concentration of weakly doped ionic systems, which in turn may lead to novel nanostructured composite materials with enhanced transport properties or, for instance, kinetics for oxygen reduction or water splitting.