Selective growth of α-Fe2O3, γ-Fe2O3 and Fe3O4 at low temperatures and under ambient pressure. (27th August 2019)

• Record Type: Journal Article
• Authors: Kan, Daisuke; Sugano, Satoshi; Kosugi, Yoshihisa; Kobayashi, Kento; Uebayashi, Nao; Koganezawa, Tomoyuki; Shimakawa, Yuichi
• Is Part Of: Japanese journal of applied physics. Volume 58:Number 9(2019)
• Publication Date: 2019-08-27
• Subjects: Physics -- Periodicals; 621.05
• DOI: 10.7567/1347-4065/ab39d1
• Languages: English
• ISSNs: 0021-4922

Abstract

Abstract: We fabricated thin films of α - and γ -Fe2 O3 and Fe3 O4 at 400 °C under ambient (non-vacuum) conditions by using a mist chemical vapor deposition (mist CVD) method and investigated their structural and physical properties. We found that the structural phases of the films with preferred orientations depend on surface structures of substrate crystals and that the valence states of Fe in the films depend on solvents in which the Fe precursor (Iron (III) acetylacetonate) was dissolved. When films are grown by atomizing aqueous solutions of the precursor, (001) α -Fe2 O3 and (001) γ - Fe2 O3, both of which have only Fe 3+, are grown on (001) Al2 O3 and (001) SrTiO3 substrates, respectively. On the other hand, when methanol-rich solutions (98% methanol and 2% water in volume) are atomized, (111) and (001)-oriented Fe3 O4 films which accommodate Fe 3+ and Fe 2+ were grown on the Al2 O3 and SrTiO3 substrates, respectively. Magnetization measurements show that the γ -Fe2 O3 and Fe3 O4 films have room temperature saturated magnetizations as large as 200 and 500 emu/cc. Furthermore, the Fe3 O4 films exhibit drastic decreases in the magnetization at 110 K, which are attributed to the Verwey transition. These results indicate that mist CVD is a nice technique that can enable one to control both crystal structures and Fe valence states in iron oxide films.