Anisotropic chemical expansion due to oxygen vacancies in perovskite films

In scientifically intriguing and technologically important multifunctional ABO(3) perovskite oxides, oxygen vacancies are most common defects. They cause lattice expansion and can alter the key functional properties. Here, it is demonstrated that contrary to weak isotropic expansion in bulk samples, oxygen vacancies produce strong anisotropic strain in epitaxial thin films. This anisotropic chemical strain is explained by preferential orientation of elastic dipoles of the vacancies. Elastic interaction of the dipoles with substrate-imposed misfit strain is suggested to define the dipolar orientation. Such elastic behavior of oxygen vacancies is anticipated to be general for perovskite films and have critical impacts on the film synthesis and response functions.

Automated summary

The study demonstrates that oxygen vacancies in ABO(3) perovskite oxides primarily result in strong anisotropic strain in epitaxial thin films, rather than weak isotropic expansion in bulk samples. This anisotropic chemical strain is explained by the preferential orientation of elastic dipoles of the vacancies, which have critical impacts on the synthesis and response functions of the films.