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

When alpha-Fe2O3 thin films are deposited on alpha-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 (11(2) over bar 0) 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 (11(2) over bar 0), 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(10(1) over bar 0) and 1/3(01(1) over bar 0) 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. (C) 2003 Elsevier Science B.V. All rights reserved.