Structural investigation of (111) oriented (BiFeO3)(1-x){\Lambda}/(LaFeO3)x{\Lambda} superlattices by X-ray diffraction and Raman spectroscopy

TL;DR

This study investigates the structural phases of (BiFeO3)(1-x){b1}/(LaFeO3)x{b1} superlattices grown on (111) SrTiO3, revealing a temperature-dependent symmetry change from rhombohedral/monoclinic to orthorhombic at x=0.5 using X-ray diffraction and Raman spectroscopy.

Contribution

It provides the first detailed analysis of phase stability and symmetry transitions in (111)-oriented BiFeO3/LaFeO3 superlattices, highlighting the role of anisotropic strain and interface compatibility.

Findings

Structural phase change at x=0.5 from rhombohedral/monoclinic to orthorhombic.

Confirmation of symmetry change through Raman spectroscopy.

Orientation-dependent phase stability influenced by strain and octahedral tilts.

Abstract

(BiFeO3)(1-x){\Lambda}/(LaFeO3)x{\Lambda} superlattices (SLs) with varying x have been grown by pulsed laser deposition on (111) oriented SrTiO3 substrates. In order to obtain good epitaxy and flat samples a conducting SrRuO3 buffer has been deposited prior to the superlattices to screen the polar mismatch for such (111) SrTiO3 orientation. X-ray diffraction reciprocal space mapping on different family of planes were collected and evidenced a room temperature structural change at x=0.5 from a rhombohedral/monoclinic structure for rich BiFeO3 to an orthorhombic symmetry for rich LaFeO3. This symmetry change has been confirmed by Raman spectroscopy and demonstrates the different phase stability compared to similar SLs grown on (100) SrTiO3. The strongly anisotropic strain and oxygen octahedral rotation/tilt system compatibility at the interfaces probably explain the orientation dependence of the phase stability in such superlattices.