Structural characterization of epitaxial LiFe₅O₈ thin films grown by chemical vapor deposition

We report on detailed microstructural and atomic ordering characterization by transmission electron microscopy in epitaxial LiFe₅O₈ (LFO) thin films grown by chemical vapor deposition (CVD) on MgO (001) substrates. The experimental results of LFO thin films are compared with those for bulk LFO single crystal. Electron diffraction studies indicate weak long-range ordering in LFO (α-phase) thin films in comparison to bulk crystal where strong ordering is observed in optimally annealed samples. The degree of long-range ordering depends on the growth conditions and the thickness of the film. Annealing experiment along with diffraction study confirms the formation of α-Fe₂O₃ phase in some regions of the films. This suggests that under certain growth conditions γ-Fe₂O₃-like phase forms in some pockets in the as-grown LFO thin films that then convert to α-Fe₂O₃ on annealing. - Highlights: • Atomic ordering in LiFe₅O₈ bulk single crystal and epitaxial thin films. • Electron diffraction studies reveal different level of ordering in the system. • Formation of γ-Fe₂O₃ like phase has been observed.