TiO2 Coating for SnO2:F Films Produced by Filtered Cathodic Arc Evaporation for Improved Resistance to H+ Radical Exposure

Abstract

Titanium dioxide thin films were deposited by filtered cathodic arc evaporation (FCAE) from a Ti target in an oxygen atmosphere onto (a) fluorine-doped tin oxide substrates SnO2:F (FTO) and (b) glass microscope slides. The growth rate calculated from film thickness profilometry measurements was found to be approximately 0.8 nm/s. The films were highly transparent to visible light. x-Ray photoemission spectroscopy analysis of the Ti 2p electron binding- energy shift confirmed the presence of a TiO2 stoichiometric compound. The results for the root-mean-square (RMS) surface roughness of the films deposited onto FTO substrates evaluated by atomic force microscopy suggested nanostructured film surfaces. When exposed to hydrogen plasma, TiO2 films revealed insignificant changes in the optical spectra. The initial sheet resistance of the SnO2:F layer was 14 Ω/sq. The deposition of the top TiO2 layer (45 nm thick) over the FTO electrode resulted in an increase of the sheet resistance of 2 Ω/sq. In addition, the sheet resistance of the double-layer FTO/TiO2 transparent conductive oxide (TCO) electrode increased by 1 Ω/sq as a result of H+ plasma exposure. Regardless of the TiO2 film’s low conductivity, a thin protective layer could be coated onto FTO films (presumably 15 nm thick) due to their high transparency, offering high resistance to aggressive H+ plasma conditions. In this paper we show that ∼50-nm-thick TiO2 coating on FTO films provides sufficient protection against deterioration of transparency and conductivity due to hydrogen radical exposure.

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Correspondence to M. M. Ristova.

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Ristova, M.M., Gligorova, A., Nasov, I. et al. TiO2 Coating for SnO2:F Films Produced by Filtered Cathodic Arc Evaporation for Improved Resistance to H+ Radical Exposure. Journal of Elec Materi 41, 3087–3094 (2012). https://doi.org/10.1007/s11664-012-2221-4

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Keywords

  • TiO2
  • thin-film coating
  • AFM
  • XPS
  • filtered cathodic arc evaporation (FCAE)
  • transmittance
  • reflectance
  • H+ radicals
  • XPS
  • SEM
  • AXRD
  • XRR