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.