Extended defects in epitaxial $Sc2O3$ films grown on (111) Si

Epitaxial $Sc2O3$ films with the cubic bixbyite structure were grown on (111) Si by reactive molecular beam epitaxy. High-resolution transmission electron microscopy (HRTEM) revealed an abrupt, reaction-layer free interface between $Sc2O3$ and Si. The $∼10%$ lattice mismatch between Si and $Sc2O3$ was relieved by the formation of a hexagonal misfit dislocation network with Burgers vectors of $1∕2⟨1¯10⟩Si$ and line directions parallel to $⟨112¯⟩Si$⁠. A high density of planar defects and threading dislocations was observed. Analysis of lattice shifts across the planar defects in HRTEM showed that these faults were likely antiphase boundaries (APBs). ABPs form when film islands coalesce during growth because films nucleate with no unique arrangement of the ordered oxygen vacancies in the bixbyite structure relative to the Si lattice.