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

Abstract

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.