Atomic-level simulations of misfit dislocation at the interface of Fe2O3/Al2O3 system

When α-Fe2O3 thin films are deposited on α-Al2O3(0 0 0 1) substrates using oxygen plasma assisted molecular beam epitaxy, a periodic distribution of basal dislocations occurs due to lattice mismatch along the interfaces. High-resolution transmission electron microscopy shows, when observed from <1120> zone axis, that these dislocations lie at the interface about 7.0 nm apart. Molecular-dynamics simulations were performed in order to understand the formation of misfit dislocations and the interface structural features in Fe2O3/Al2O3 system. It is found that the misfit dislocations are mainly formed in Al2O3 substrates with Burger’s vector of 1/3<1120>, and terminated at the interfaces, in consistent with experiments observed previously. These dislocations can dissociate into two partial dislocations with Burger’s vectors of 1/3<1010> and 1/3<1010> by forming stacking faults on (0 0 0 1) planes. The core structures of the misfit dislocations in semicoherent interfaces are analyzed in detail, and the misfit dislocations have narrow cores in the plane of the interfaces.