Structural, optical and electrical properties of undoped polycrystalline hematite thin films produced using filtered arc deposition

Thin films of alpha-Fe2O3 (hematite) were deposited using filtered arc deposition. The structural, optical and electrical properties of the films have been characterized. High-purity hematite films were produced, free from other iron oxide phases and impurities. The films exhibit preferred orientation, with the c-axis of the hexagonal structure aligned perpendicular to the substrate. The films have an upper uncertainty bound of the porosity of 15%, with a micro indentation hardness of 17.5 +/- 1 GPa and elastic modulus of 1235 +/- 5 GPa. The indirect and direct band gap energies were found to be approximately 1.9 eV and 2.7 eV, respectively. The refractive index, and the extinction and absorption coefficients were determined from total reflectance and direct transmittance measurements. The thin films exhibit a high resistivity (>= 10(5) Omega cm) which indicates pure alpha-Fe2O3. An activation energy of 0.7 eV was calculated from an Arrhenius plot of the conductivity. Crown Copyright (c) 2007 Published by Elsevier B.V. All rights reserved.