Regensburg 2007 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 7: Dielectric and Ferroelectric Thin Films and Nanostructures I
DF 7.7: Vortrag
Dienstag, 27. März 2007, 16:50–17:10, H11
Impedance spectroscopy of thin (d ≈ 4 (nm)) tantalum oxide films: Temperature and Field dependence — •Katrin Bruder1, Achim Walter Hassel1, Beate Mildner2, and Detlef Diesing2 — 1Max-Planck-Institut für Eisenforschung, Max-Planck-Str. 1, 40237 Düsseldorf — 2Institut für physikalische Chemie, Universität Duisburg-Essen, 45141 Essen
Impedance spectroscopy of tantalum oxide films was accomplished in thin film capacitors (tantalum–tantalum oxide–noble metal). With investigations from f=10−2 Hz to 10+6 Hz it is possible to determine the capacitance, the metals resistivities and the tunnel resistivity of the oxide. The latter one is a function of the bias voltage while the capacitance and the metals resistivities remain unchanged. The tunnel resistivity was found to have a maximum at a bias Umax slightly different from 0 V. Within single band tunneling models Umax ≡ 0 V is expected whereas two band tunneling models were found to deliver Umax ≠ 0 V as function of the barrier asymmetry and the oxides band gap. For a further investigation the bias dependence of impedance spectra was characterised in the temperature range from T = 58 K to 350 K. Umax was found to vary with T. A comparison with theory points to a temperature dependent barrier asymmetry of the oxide.