Effect of nitrogen dioxide on titanium bisphthalocyaninato thin films

Thin films of Titanium bis-phthalocyaninato (TiPc2) are deposited on interdigital electrodes by evaporation under vacuum and have been investigated as semiconducting gas sensors. Oxidation of the films by NO2 is studied by visible absorption spectroscopy and IR spectroscopy of neutral and oxidised films. The variation at room temperature (RT) of electrical conductivity with different concentrations of NO2 has been investigated. The results describe the existence of a conductivity maximum during the oxidation. The analysis of the optical spectra of TiPc2 during NO2 adsorption and desorption gives the possibility to explain the change of the conductivity in terms of concentration of species present in the reaction. (C) 1998 Elsevier Science S.A. All rights reserved.