Abstract
This study investigates the impact of extended defects such as dislocations on the electronic properties of SrTiO3 by using a 36.8° bicrystal as a model system. In order to evaluate the hypothesis that dislocations can serve as preferential reduction sites, which has been proposed in the literature on the basis of ab initio simulations, as well as on experiments employing local-conductivity atomic force microscopy (LC-AFM), detailed investigations of the bicrystal boundary are conducted. In addition to LC-AFM, fluorescence lifetime imaging microscopy (FLIM) is applied herein as a complementary method for mapping the local electronic properties on the microscale. Both techniques confirm that the electronic structure and electronic transport in dislocation-rich regions significantly differ from those of undistorted SrTiO3. Upon thermal reduction, a further confinement of conductivity to the bicrystal boundary region was found, indicating that extended defects can indeed be regarded as the origin of filament formation. This leads to the evolution of inhomogeneous properties of defective SrTiO3 on the nano- and microscales.
Highlights
Strontium titanate (SrTiO3 ) is a prototype of a perovskite ternary oxide with mixed ionic-electronic conductivity [1]
To directly investigate the electronic properties of dislocation-rich grain boundaries, we investigate commercially available large-angle SrTiO3 bicrystals
In order to obtain information about the in-plane and out-of-plane distribution of the conductivity, we present local-conductivity atomic force microscopy (LC-AFM) maps of the polished surface above the grain boundary, as well as cross-sections of bicrystals, which were perpendicularly cleaved to the original surface
Summary
Strontium titanate (SrTiO3 ) is a prototype of a perovskite ternary oxide with mixed ionic-electronic conductivity [1] It is of particular interest as an electrode material for solid oxide cells, which convert electrical energy to chemical energy and vice versa [2,3,4,5,6]. It has been elaborated that extended defects such as dislocations can serve as preferential reduction sites as the formation energy of oxygen vacancies is locally significantly lowered due to lattice distortion [11,12] This implies that the electronic properties are Crystals 2020, 10, 665; doi:10.3390/cryst10080665 www.mdpi.com/journal/crystals
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