Atmospheric pressure chemical vapour deposition of Cr2−xTixO3 (CTO) thin films (≤3 µm) on to gas sensing substrates

Abstract

Atmospheric pressure chemical vapour deposition (APCVD) of CrO₂Cl₂ and TiCl₄ as precursors in the presence of an oxygen source (oxygen, water, ethyl acetate, methanol, ethanol) results in the simple, reproducible and rapid preparation of thin (≤3 µm) Cr_2−xTi_xO₃Cl_y films (x = 0.01, 0.05, 0.10, 0.16, 0.4; y = 0.1−0.3) on prefabricated sensor substrates. Annealing of films at 600 °C for 1 h under a flow of 5% H₂ in N₂ led to single phase Cr_2−xTi_xO₃ films (x = 0.01, 0.05, 0.10, 0.16, 0.4). Use of Ti(OPrⁱ)₄ instead of TiCl₄ gave a change in thin-film stoichiometry and microstructure for similar reaction conditions. The synthesis affords a high throughput route to substrate adherent layers with controlled microstructure and stoichiometry. Film characterisation was carried out using SEM, Raman spectroscopy, EDXA, XPS and the determination of the activation energy of conductance. The gas sensor response of the Cr_2−xTi_xO₃ films to ethanol is reported.