Effect of intrinsic point defects on ferroelectric polarization behavior of SrTiO3

The effect of a variety of intrinsic defects and defect clusters in bulk and thin films of SrTiO3 on ferroelectric polarization and switching mechanisms is investigated by means of density-functional-theory based calculations and the Berry phase approach. Our results show that both the titanium Ti-Sr(center dot center dot) and strontium Sr-Ti() Ti antisite defects induce ferroelectric polarization in SrTiO3, with the Ti-Sr(center dot center dot) defect causing a more pronounced spontaneous polarization and higher activation barriers of polarization reversal than Sr-Ti(). The presence of oxygen vacancies bound to the antisite defects can either enhance or diminish polarization depending on the configuration of the defect pair, but it always leads to larger activation barriers of polarization switching as compared to the antisite defects with no oxygen vacancies. We also show that the magnitude of spontaneous polarization in SrTiO3 can be tuned by controlling the degree of Sr/Ti nonstroichiometry. Other intrinsic point defects such as Frenkel defect pairs and electron small polarons also contribute to the emergence of ferroelectric polarization in SrTiO3.