Structure and orbital ordering of ultrathin LaVO3 probed by atomic resolution electron microscopy and Raman spectroscopy

Orbital ordering has been less investigated in epitaxial thin films, due to the difficulty to evidence directly the occurrence of this phenomenon in thin film samples. Atomic resolution electron microscopy enabled us to observe the structural details of the ultrathin LaVO3 films. The transition to orbital ordering of epitaxial layers as thin as ≈4 nm was probed by temperature‐dependent Raman scattering spectroscopy of multilayer samples. From the occurrence and temperature dependence of the 700 cm–1 Raman active mode it can be inferred that the structural phase transition associated with orbital ordering takes place in ultrathin LaVO3 films at about 130 K. Orbital ordering is a fascinating ordering phenomenon that has been largely studied in bulk perovskite LaVO3crystals. Here the authors address whether the orbital ordering occurs also in ultrathin epitaxial LaVO3 films. Raman scattering spectroscopy enabled us to probe the orbital ordering in 4 nm thick LaVO3epitaxial layers and to observe the occurrence of the 700 cm–1 Raman active mode below 130 K, which is indicative of the phase transition.