Hg-doped TiO2 nanostructures thin film prepared by sol-gel method for gas sensing applications: Correlation between the structural and electrical properties

Hg-doped TiO2 and undoped thin films have been synthesized from mercury acetate and titanium tetrabutyl-orthotitanate precursors deposited on silicon substrates using a sol-gel dip-coating technique. Annealing temperatures and layer thickness were found crucial for thin films nanostructures morphology which was characterized by X-ray diffraction (XRD), Raman and FTIR spectroscopy, Scanning electron microscopy (SEM) and Atomic force microscopy (AFM). XRD, Raman and FTIR results show that the 5% Hg doping shows crystallization at lower annealing temperatures. After heat treatments of thin films at 450 degrees C, the anatase-rutile transformation takes place with annealing temperature. The average crystallite size of the doped TiO2 films was increased with annealing temperature and was about 20 nm. SEM and AFM reveal nanostructures surface agglomerates of TiO2 doped Hg nanoparticles arranged with preferred orientation. The electrical properties of TiO2 doped thin films were investigated by current-voltage (I-V) characteristics. These nanostructures arrays exhibit excellent sensitivities with the increase of CO2 concentration at room temperature. Current-voltage analysis indicated that the enhanced gas sensitivity is probably due to the high surface/volume ratio of this nanostructure material in combination with the remarkable effect of Hg doping in TiO2. (C) 2015 Elsevier GmbH. All rights reserved.