High-resolution EELS on high-entropy perovskite oxide thin films
The properties of perovskites are defined by the elements on the A- and B-site. They can be influenced via the high-entropy concept by substituting the A- or B-site with five or more different elements in equiatomic ratio. Many high-entropy perovskites have been synthesized as bulk but only a few of them have been grown as thin films, where the properties can differ. (La0.2Nd0.2Gd0.2Sm0.2Y0.2)MnO3 is a manganese based high-entropy perovskite with an orthorhombic structure, which has been synthesized as powder but not as thin film. We have grown thin films of the high-entropy perovskite oxide (La0.2Nd0.2Gd0.2Sm0.2Y0.2)MnO3 on SrTiO3(001) substrates by pulsed laser deposition. By high-resolution dark field scanning transmission electron microscopy (DF-STEM), the structure was confirmed. Furthermore, the high-entropy character of the A-site with an ordered manganese lattice on the B-site was visualized by electron energy loss spectroscopy (EELS) on atomic scale on samples with 7-8 nm thickness prepared by focused ion beam technique (FIB). Different experimental approaches with conventional EELS spectrometers, as well as rapid, direct-electron counting systems are discussed and compared regarding their capabilities. Results from a single scan, as well as dose-fractionated acquisition of multiple frames to minimize beam damage to the sample, with challenging drift correction of the periodic lattice, are presented.