Short communicationPreparation of highly (001)-oriented α-Fe2O3 film on Si-substrate from drop coated BaFe12O19 via barium diffusion-induced transformation

Oriented iron oxide structure is of particular importance in electronic, magnetic, and catalytic applications. We report on a facile route to prepare (001)-oriented hematite (α-Fe2O3) film on a silicon substrate with drop coated BaFe12O19 nanoplates from hydrothermal process as precursor. The obtained α-Fe2O3 film displays an ultrahigh (001) orientation of 99.4% when treated at 1300 °C for 5 h. Transformation of BaFe12O19 into α-Fe2O3 is driven by directional diffusion of barium into the interface between BaFe12O19 coating and the substrate, where a thermodynamically stable barium silicate was produced. Given the structural similarity between BaFe12O19 and α-Fe2O3, the crystallographic direction of BaFe12O19 [001] is topologically converted into α-Fe2O3 [001] during the transformation. The ultrahigh degree of orientation of the α-Fe2O3 film is attributed to the large aspect ratios of the starting BaFe12O19 nanoplates, which facilitate the realignment of plates, causing them to flatten on the substrate during heat treatment.