Microstructural, optical and electrical properties of GeO2 thin films prepared by sol-gel method

GeO2 thin films were prepared by sol-gel method on ITO/Glass substrate. The electrical and optical properties and the microstructures of these films were investigated with special emphasis on the effects of an annealing treatment in ambient air. The films were annealed at various temperatures from 500 degrees C to 700 degrees C. Structural analysis through X-ray diffraction (XRD) and atomic force microscope (AFM) showed that surface structure and morphological characteristics were sensitive to the treatment conditions. The optical transmittance spectra of the GeO2/ITO/Glass were measured using a UV-visible spectrophotometer. All films exhibited GeO2 (101) orientation perpendicular to the substrate surface where the grain size increased with increasing annealing temperature. The optical transmittance spectroscopy further revealed high transparency (over 70%) in the wave range 400 - 800 nm of the visible region. At an annealing temperature level of 700 degrees C, the GeO2 films were found to possess a leakage current density of 1.31x10(-6) A/cm(2) at an electrical field of 20 kV/cm. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim