Assessment of Strain-Generated Oxygen Vacancies Using SrTiO₃ Bicrystals

Abstract

Atomic-scale defects strongly influence the electrical and optical properties of materials, and their impact can be more pronounced in localized dimensions. Here, we directly demonstrate that strain triggers the formation of oxygen vacancies in complex oxides by examining the tilt boundary of SrTiO3 bicrystals. Through transmission electron microscopy and electron energy loss spectroscopy, we identify strains along the tilt boundary and oxygen vacancies in the strain-imposed regions between dislocation cores. First-principles calculations support that strains, irrespective of their type or sign, lower the formation energy of oxygen vacancies, thereby enhancing vacancy formation. Finally, current-voltage measurements confirm that such oxygen vacancies at the strained boundary result in a decrease of the nonlinearity of the I-V curve as well as the resistivity. Our results strongly indicate that oxygen vacancies are preferentially formed and are segregated at the regions where strains accumulate, such as heterogeneous interfaces and grain boundaries.

Room-Temperature Plastic Deformation of Strontium Titanate Crystals Grown from Different Chemical Compositions

“…In general, point defects act as barriers to dislocation motion and result in work hardening of materials followed by nucleation and growth of cracks, leading to brittle fracture. In fact, both Sr and O vacancies have been reported to be present around dislocations in SrTiO 3 [14][15][16], forming a Cottrell atmosphere [1]. However, the influence of point defects on the dislocation mobility in SrTiO 3 has not been examined.…”

Thermomechanical stabilization of electron small polarons in SrTiO3 assessed by the quasiharmonic approximation

“…This quantity is fundamental because it both dictates the chemical expansivity [19,20] and is related directly to the absolute deformation potentials of the conduction and valence bands in the case of free electrons and holes, respectively [18,19]. Finally, it is well established that mechanical stresses and strains can substantially alter the concentration [21,22] and mobility of both ionic [23] and electronic defects [24] in semiconductors and insulators. In spite of this, there are few reported studies examining the effects of mechanical stress on the degree of localization of the electronic defects [25].…”

Nanoionics and interfaces for energy and information technologies

“…The high degree of structural disorder found in the different types of grain boundaries can influence on the defect chemistry of the material, leading to a local change in its chemical composition. Many studies have found that oxygen vacancies are created within the firsts atomic planes in several oxides [14][15][16][17][18][19][20][21]. For example, An and co-workers analysed an 8% mol.…”