Microstructural investigation of strontium titanate films grown by interval pulsed laser deposition

Strontium titanate (SrTiO3) films were deposited on (001) magnesium oxide (MgO) substrates by pulsed laser interval deposition (PLID). The growth modes of the films were monitored by in-situ reflection high-energy electron diffraction (RHEED). The microstructures were investigated by transmission electron microscopy (TEM). It has been shown that PLID can enhance the two dimensional (2D) growth of this system, which has the large lattice misfit of 7.9%. The addition of a mono TiO2 buffer layer to the MgO substrate surface further improved the 2D growth mode. TEM results revealed that the films grown in 2D mode with large lattice mismatch were dominated by antiphase boundaries (APBs) and holes. All the holes were connected by antiphase boundaries. The holes were rectangular in shape, with facets along the [100] and [010] directions, and they ran though the whole film thickness. Threading and misfit dislocations have also been identified as growth defects in the films grown with and without a TiO2 buffer layer. However, the density of defects varies with growth mode.