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DF: Fachverband Dielektrische Festkörper

DF 19: Poster 2

DF 19.4: Poster

Mittwoch, 13. März 2013, 15:00–17:30, Poster B2

Voltage-dependent impedance analysis of metal/ta-C/Si heterostructures — •Julian Alexander Amani, Tristan Koppe, Hans Hofsäss, and Ulrich Vetter — II. Physikalisches Institut, Georg-August-Universität Göttingen, Deutschland

Whether tetrahedral amorphous carbon (ta-C) is used as electrode coating for electrochemical impedance spectroscopy (EIS) or as coating on medical implants, knowledge of its impedance properties is essential.

Different electrical equivalent circuits (EECs) have been proposed to reproduce the electrical properties of ta-C, so far, ignoring the knowledge of the voltage-dependence of its DC conductivity. Considering voltage-dependence of elements in an EEC facilitates correct assignment of circuit components to different parts of the investigated system and, hence, permits selection of the EEC with most accurate description of the underlying physics.

In this work, voltage-dependent impedance spectra were measured and compared to simulations, eliminating the ambiguity of the different proposed circuits. It could be shown that a Voigt-type circuit of a voltage-dependent resistance and a voltage-independent constant-phase element (CPE) describes the ta-C layer correctly. In contrast to most impedance analyses, the voltage- and frequency-dependence of the system was calculated and compared to the measured values in the complete parameter-space, not only for a single frequency spectra at each bias voltage separately. Possibility of large-signal analysis in time-domain allowed realistic simulations of the extremely non-linear resistive behaviour of ta-C.