Berlin 2012 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 37: Topical Session Modern Atom Probe Tomography I - Fundamentals

MM 37.4: Talk

Wednesday, March 28, 2012, 16:15–16:30, H 0107

Atom probe tomography of solid state ion-conductive membranes — •Gerd-Hendrik Greiwe, Frank Berkemeier, Zoltan Balogh, and Guido Schmitz — Institut für Materialphysik WWU Münster, Münster, Germany

We could demonstrate that thin film membranes of amorphous Li-borate reveal a better conductivity than quenched bulk glasses (1). We measured the Li content by atom probe tomography. Layers of Li-borate and Li-silicate glasses were deposited upon tungsten tips. Although complex, the mass spectra are well understood in terms of various molecular species allowing a quantitative analysis. New effects at the interfaces were observed, that can be explained with the dielectric and ion-conductive properties of the glasses. By applying a base voltage to the specimen during the measurement, we create an electric field over the glass layer. Mobile Li ions redistribute to compensate the field. Therefore, we measure increased Li concentration at the surface and a depleted zone at the layer/substrate interface.

Using a model of field penetration and band bending by Tsong (2) we calculated the resulting electric field in the layers and its effect on the diffusion of the Li ions. This model predicts a field penetration of a few angstroems, forming a space charge surface layer. The calculations show reasonable agreement with the measurements, thus confirming the model.

(1) F. Berkemeier, M.R. Abouzari, G. Schmitz, Ionics, 15 (2009) 241

(2) T.T. Tsong Surface Science 82 (1979) 28-42