Ordering in (La,Sr)(Al,Ta)O₃ substrates

(La, Sr)(Al, Ta)O₃ (LSAT) has recently received increased attention as a substrate for the deposition of various oxide films. LSAT is usually considered as having a perovskite structure. However, the exact atomic structure of LSAT is not yet well known and has received little attention up to now. In this paper, a series of studies using x-ray diffraction, transmission electron microscopy, and energy dispersive spectrometry were conducted to determine the atomic structure of LSAT. It was found that LSAT consists of two types of domains: one with a simple cubic perovskite structure (disordered with a = 0.3868 nm) and the other with a face-centered-cubic structure (ordered with a = 0.773 nm). Computer image simulation of high-resolution lattice images suggests that the ordered structure is due to ordering of the Al and Ta ions.