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DF: Fachverband Dielektrische Festkörper
DF 18: Applications of dielectric solids
DF 18.1: Talk
Thursday, March 17, 2011, 16:00–16:20, MÜL Elch
Nanometer thin tantalum oxide capacitors: Characterization of temperature stability and built in electric fields. — •Katrin Bruder1, Kevin Stella2, and Detlef Diesing2 — 1Heraeus Clevios GmbH, Chempark Leverkusen — 2Fakultät für Chemie, Universität Duisburg-Essen, D-45117 Essen, Germany
Tantalum oxide based capacitors are widely used in electronic applications. A big amount of works exists for thicker oxide films d>10 nm. However, for the production of high capacitance values per area thinner oxide films d< 10 nm are of significant interest since the capacitance scales with d−1. We present current-voltage experiments with 2 to 5 nm thick tantalum oxide capacitors. The temperature of the devices was varied from 40 K to 500 K. To avoid degradation of the devices the experiments were carried out under ultra high vacuum conditions. Tantalum oxide capacitors were found to be stable in the mentioned temperature range. By monitoring the temperature and voltage dependence of the device current one can determine the built in electric field Ebuilt−in=0.15 V/nm. Deviations from the bulk dielectric behaviour were found for the dielectric permittivity єrel. Thin films only show values from 8 to 12 in contrast the bulk value of 28. This finding is attributed to asymmetric dipole layers at the oxide interfaces and smeared out band edges inside the vitreous oxide film. The asymmetry of the dipole layers may also evoke the built-in electric field.