Probing orbital ordering in LaVO3 epitaxial films by Raman scattering

Abstract

Single crystals of Mott-Hubbard insulator LaVO3 exhibit spin and orbital ordering along with a structural change below ≈140 K. The occurrence of orbital ordering in epitaxial LaVO3 films has, however, been little investigated. By temperature-dependent Raman scattering spectroscopy, we probed and evidenced the transition to orbital ordering in epitaxial LaVO3 film samples fabricated by pulsed-laser deposition. This opens up the possibility to explore the influence of different epitaxial strain (compressive vs. tensile) and of epitaxy-induced distortions of oxygen octahedra on the orbital ordering, in epitaxial perovskite vanadate films.

Unraveling the enhanced Oxygen Vacancy Formation in Complex Oxides during Annealing and Growth

“…For the deposition of fully oxygenated thin films, a high oxygen pressure is necessary to either compensate or inhibit the oxygen ejection from the thin film induced by the high energetic species of the plasma plume. At the same time some oxides require a low oxygen pressure during deposition in order to guarantee a low valence state of the involved cations1213, or to obtain layer-by-layer growth, as high physical pressures result in 3D growth101415. Thus when aiming for high quality heterostructures or superlattices the competition of crystalline perfection and stoichiometry limits the choice of materials and the achievable interface quality101617.…”

Structure and orbital ordering of ultrathin LaVO3probed by atomic resolution electron microscopy and Raman spectroscopy

“…S2). These two directions could be assigned from the analysis of the two different FFT patterns (see insets) , considering the positions of the extra spots yielded by an orthorhombic Pbnm structure (marked by the white hollow arrows shown on the FFT patterns). Because the La 0.75 Sr 0.25 VO 3 layers are almost cubic ( vide infra ), they cannot yield these extra spots.…”

“…Epitaxial films and multilayers were fabricated by PLD using a KrF excimer laser for laser ablation, as we previously reported . Twinned LaGaO 3 (110)/(001) O single crystal substrates were employed for the epitaxial growth.…”

“…S1). The Raman scattering signal belonging to the epitaxial films or multilayers was obtained by normalizing the two spectra and their subsequent subtraction .…”

“…Below T OO ≈ 140 K, the oxygen stretching mode arising from the crystal distortion coupled with the G‐type OO contributes to the Raman scattering spectra around 700 cm −1 and serves as a very convenient way to probe the occurrence of the OO phase transition. Recently by temperature‐dependent Raman scattering spectroscopy we probed and evidenced the transition to orbital ordering in relatively thick (55 nm) epitaxial LaVO 3 film samples grown by pulsed‐laser deposition (PLD) on various single crystal substrates . Here we address whether the orbital ordering and the structural phase transition occur also in ultrathin epitaxial films, as thin as about 4 nm.…”