Berlin 2005 – scientific programme

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AKB: Biologische Physik

AKB 200: Poster Session II

AKB 200.67: Poster

Tuesday, March 8, 2005, 17:00–19:00, Poster TU C

Characterization of High-K Coatings on Silicon Chips in Electrolyte for Capacitive Stimulation of Nerve Cells — •Frank Wallrapp und Peter Fromherz — Max Planck Institute of Biochemistry, Martinsried, Germany

Non-invasive capacitive stimulation of neurons is commonly achieved from silicon chips insulated by a thin layer of SiO₂. Higher capacitances of the chips however would facilitate stimulation. We therefore replaced SiO₂ by the high-k materials HfO₂ and TiO₂. Capacitance and leakage current were measured in an electrolyte-insulator-silicon (EIS) configuration. Considering leakage current and biocompatibility, HfO₂ and TiO₂ both proved to be as suitable for neuronal stimulation as SiO₂. Due to the higher capacitance, TiO₂ is superior in applications. For all materials, the dielectric constant, interfacial layer thickness and charge trapping properties were examined. The capacitance vs. voltages (CV) curves of SiO₂ and HfO₂ were explained by standard metal-insulator-semiconductor (MIS) theory. Those of TiO₂ exhibited some unique features which we were able to rationalize by treating the TiO₂ explicitly as a wide band-gap semiconductor. The new high-k coated chips have opened up the way to new applications, e.g. opening voltage-gated channels in HEK293 cells and stimulating rat brain slices.