Dislocation network driven structural relaxation in hematite thin films

Using surface X-ray diffraction, we investigated 20 nm thick α-Fe2O3(0 0 0 1) thin films deposited on α-Al2O3(0 0 0 1) and Pt(1 1 1) single crystals. The films were grown in identical conditions by atomic oxygen assisted molecular beam epitaxy techniques. Both substrates offer close lattice parameter misfits. On sapphire an isostructural epitaxial relationship is observed and a 30°° in plane rotation of the lattice for Pt(1 1 1). The crystalline quality of the film deposited on Pt(1 1 1) is much better and contained less parasitic contributions. The improved crystalline quality of α-Fe2O3(0 0 0 1) layers on Pt(1 1 1) is attributed to the presence of a very well ordered interfacial dislocation network which is missing when α-Al2O3 is used as substrate.