Dresden 2011 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
DS: Fachverband Dünne Schichten
DS 43: Poster II: Thin Film Chalcogenide Photovoltaics; Thermoelectric Materials, Thin Films, and Nanostructures
DS 43.19: Poster
Mittwoch, 16. März 2011, 15:00–17:30, P2
Percolation in a CuO / CuS System — •Jörg Hennemann1, Tilman Sauerwald1, Claus-Dieter Kohl1, Julia Dräger2,3, Stefanie Russ2 und Armin Bunde3 — 1Institut für Angewandte Physik, Justus Liebig Universität Gießen, Germany — 2Institut für Theoretische Physik, Freie Universität Berlin, Germany — 3Institut für Theoretische Physik III, Justus Liebig Universität Gießen, Germany
We investigate the change of conductance in CuO thin films during exposure to H2S and interpret this change in the framework of the percolation model. We prepared a 50 nm copper film by thermal vapour deposition. The film was thermally oxidized to CuO at 250 ∘C. Then samples were exposed to H2S in air (15, 20 and 25 ppm) at 200 ∘C. The conductance remains unchanged for 5 to 10 min followed by a sudden steep increase over 2 orders of magnitude within 1 min. We assume a successive phase transition from covellite CuO to tenorite CuS. EDX analysis verifies an increase of sulfur within the film during the gas exposure. SEM analysis shows a growth of clusters during the gas exposure and an analysis by AFM shows that these clusters are connected. The rise of conductance has typical power law characteristics for percolation systems as we show with Monte Carlo simulation in 2D site percolation systems. The experimentally observed power law exponent leads to an anomalous diffusion exponent dw ≈ 2.5 in the corresponding diffusional process. This percolation effect could be interesting for gas sensor applications.