Strontium vacancy clustering in Ti-excess SrTiO_3 thin film

摘要

The defect structure of a homoepitaxial thin film of SrTiO_3 containing excess Ti grown by pulsed laser deposition is investigated. The Sr/Ti ratio of the film is controlled to possess a slight excess of Ti by tuning the laser fluence. High-resolution transmission electron microscopy and electron energy loss spectroscopy studies reveal that the film contains Sr vacancies because of the presence of excess Ti. These vacancies tend to cluster as platelets several nanometers in diameter on (001) planes in the films. The SrO planes that contain the vacancy clusters exhibit lattice expansion due to Coulomb repulsion.