Optical properties of In2O3 thin films prepared by rf helicon magnetron sputtering

Polycrystalline In2O3 films with cubic crystal structure and film thicknesses of 239, 472, 579 and 745 nm respectively were grown on quartz substrates at substrate temperature 450 degrees C by rf helicon magnetron sputtering. The preferred crystal growth orientation is varied from < 111 > to < 211 > with increasing film thickness as confirmed by X-ray diffractometry. The photon energy dependent optical properties such as complex dielectric functions and absorption coefficient, optical band gap, and Urbach energy width of the samples have been obtained from spectroscopic ellipsometry analysis in the energy range from 1.5 eV to 5.0 eV. The relation between those optical properties and crystal structure and/or crystallinity of the films was discussed. The band gap value, which is averaged over two typical samples with good crystallinity, is 3.765 eV and agrees satisfactorily with reported value on that of single crystal. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim