TiO2 thin films doped with Pd and Eu for optically and electrically active TOS-Si heterojunction

Abstract

In this work, optical and electrical characterization of transparent Eu and Pd-doped TiO2 thin films has been presented. Thin films of TiO2 doped with Eu (0.9 at.%) and Pd (5.8 at.%) were deposited on silicon and glass substrates from Ti-Eu-Pd mosaic target using modified magnetron sputtering method. X-ray diffraction measurements revealed nanocrystalline structure with the only rutile phase of TiO2 in prepared thin films. Pd-doping, through formation of discontinuous paths for charge carriers brings the enhanced electrical conductivity and makes prepared thin films oxide semiconductors. It has been shown, that Eu dopant acts as an optical activator of light conversion from UV to the red-visible, corresponding to the optical working range of standard silicon devices. From electrical measurements it was found out that Eu-doping of TiO2 results in the n-type of electrical conduction. From optical transmission spectroscopy measurements position of the fundamental absorption edge and optical band-gap energy have been determined. The current to voltage dependence and photovoltage observations confirmed the formation of heterojunction at thin film-silicon interface. © 2008 Elsevier B.V. All rights reserved.