Berlin 2015 – scientific programme

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DS: Fachverband Dünne Schichten

DS 4: Thin Film Characterisation II: Structure Analysis and Composition

DS 4.8: Talk

Monday, March 16, 2015, 16:45–17:00, H 0111

Modification of energy band alignment and electric properties of Pt/Ba_0.6Sr_0.4TiO₃/Pt thin-film ferroelectric varactors by Ag impurities at interfaces — Stefan Hirsch, •Philipp Komissinskiy, Stefan Flege, Shunyi Li, Karsten Rachut, Andreas Klein, and Lambert Alff — Institute for Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt, Germany

We report on the effects of Ag impurities at interfaces of parallel-plate Pt/Ba_0.6Sr_0.4TiO₃/Pt thin film ferroelectric varactors. Ag impurities occur at the interfaces due to diffusion of Ag from colloidal silver paint used to attach the varactor samples with their back side to the plate heated at 600-750 ^∘C during deposition of Ba_0.6Sr_0.4TiO₃. X-ray photoelectron spectroscopy and secondary ion mass spectrometry suggest that amount and distribution of Ag adsorbed at the interfaces depend strongly on the adsorbent surface layer. In particular, Ag preferentially accumulates on top of the Pt bottom electrode. The presence of Ag significantly reduces the barrier height between Pt and Ba_0.6Sr_0.4TiO₃ leading to an increased leakage current density and, thus, to a severe degradation of the varactor performance.
S. Hirsch, P. Komissinskiy, S. Flege, S. Li, K. Rachut, A. Klein, and L. Alff, J. Appl. Phys. 115, 243704 (2014).