Structural and Optical Properties of Epitaxial Iron Oxide Thin Films Deposited by Pulsed Laser Deposition

Iron oxides have been intensively studied owing to potential applications related to energy conversion and storage systems. In this paper, we investigated crystal structures and optical properties of iron oxide thin films deposited at various oxygen partial pressures and temperatures using pulsed laser deposition. The iron oxide thin films were epitaxially grown on Al₂O₃ (0001) substrates confirmed by X-ray diffraction measurements. With increasing the growth temperature from 450 K to 800 K, the films exhibited better crystalline hematite phase, alpha-Fe₂O₃. When the pressure was decreased to 0.5 mTorr, the magnetite phase, Fe₃O₄, was formed. We found that the optical band gaps of iron oxides mainly originated from O 2p to Fe 3d could be modulated from 2.18 eV to 2.42 eV, applicable for energy conversion systems.