Influence of misfit dislocations on the phase transition of iron(iii) oxides

Abstract

Dislocations commonly occur in thin films under large misfit strain due to the accumulation of strain energy, significantly altering the films' properties. This study investigates the microstructure of Fe₂O₃ polymorphs in films of various thicknesses deposited on yttria-stabilized zirconia (001) substrates. The results reveal that the ε-Fe₂O₃ phase is formed and stabilized at thicknesses below a critical threshold of 20 nm. Beyond this threshold, the volume fraction of the ε-Fe₂O₃ phase decreases, and the α-Fe₂O₃ phase begins to emerge. With further increases in thickness, the ε-Fe₂O₃ phase fully transforms into the α-Fe₂O₃ phase. Detailed analysis suggests that this phase transformation is driven by the formation of misfit dislocations at the film/substrate interface, which compensates for the tensile strain induced by the substrate.