Theoretical studies of defects in oxide thin films

Coherent epitaxial strain in thin films and heterostructures can not only induce changes in the crystal structure but also affect the defect population within the thin-film material. The effect can be understood in terms of redox reactions that accompany defect formation and lead to changes of the ionic radii around the defect. This talk will give an overview of the basic defect chemistry in strained materials, based mostly on results from density functional theory (DFT) calculations and highlight experimental observations of this coupling between mechanical deformation and the stoichiometry. We will also show how the charge state of a defect or more generally the valence of ions can be affected by different biaxial and isostatic strain states.