Barrier layers and functional/ structured surfaces

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Transparent flexible semiconductor thin film (titanium (IV) oxide) on polymer foil
Transparent conductive film
with gas permeation barrier:
Graphene/silicon(IV) oxide/PET

Low-temperature processes for preparation of metal oxide thin films

Inorganic metal oxide thin films (20-200 nm thick) are prepared from suitable molecular precursors (e. g. metal-organic compounds) via UV-initiated reactions. These thin films are applicable as gas permeation barriers for encapsulation of photovoltaic modules or organic light emitting diodes.

This synthesis route offers the following advantages:


  • Applicable close to normal temperature and pressure
  • Use of commercially available UV light sources
  • Precursor deposition by conventional methods
  • Inorganic coating on thermally sensitive substrates (e.g. polyester films)
  • Usually a high adhesion of the inorganic layers on organic polymeric substrates is achieved


Selected research and development activities of the group involves:


  • Mechanistic investigations on the photochemical conversion of metal-organic compounds (combination of experiment and theory - DFT calculations)
  • Thin film analytics
  • Increasing the energy efficiency (kinetics) of UV-initiated reactions via tuning of wavelength regarding  precursor compounds
  • Thin-film deposition on flexible substrates and assessment of application potential
  • Further modification of the inorganic layers with organic films (e.g. for the large-scale transfer of the 2D material graphene, demonstrated in the EU FP7 project GLADIATOR)

Very homogeneous and defect-free layers with thicknesses in the lower nanometer range can be produced by Atomic Layer Deposition (ALD) even at low deposition temperatures. This method allows to deposition films on substrates with very complex 3-dimensional geometries and high aspect ratios.


Selected Publications:

  • P. C. With, U. Helmstedt, S. Naumov, A. Sobottka, A. Prager, U. Decker, R. Heller, B. Abel, L. Prager Low-Temperature Photochemical Conversion of Organometallic Precursor Layers to Titanium(IV) Oxide Thin Films
    Chemistry of Materials 2016, 28, 7715

  • L. Wennrich, H. Khalil, C. Bundesmann, U. Decker, J. W. Gerlach, U. Helmstedt, D. Manova, S. Naumov, L. Prager
    Photochemical preparation of aluminium oxide layers via vacuum ultraviolet irradiation of a polymeric hexanoato aluminium complex
    Materials Chemistry and Physics 2013, 137, 1046