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Metal-Insulator-Metal Gas Sensor Based on Polarizable Thin Films

Authors:
Martin Schreivogel
Denis Kunz
Ralf-Roman Rosenberger
Wolfgang Menesklou
Ellen Ivers-Tiffée

Keywords: gas sensor; hydrogen; silicon dioxid; aluminum oxid; polarization; impedance spectroscopy

Abstract:
A new type of Metal-Insulator-Metal (MIM) gas sensor sensitive to low concentrations of hydrogen containing gases is presented. Less than 5 ppm H2 give rise to significant signal changes compared to pure nitrogen or air. Response times are in the order of several ten seconds. The capacitive structure incorporates two stacked dielectric thin films (SiO2, Al2O3) with a thickness of a few ten nanometers sandwiched between platinum electrodes. The oxides show a distinct polarization mechanism that influences the dielectric properties of the films at elevated temperatures above 200 °C. The devices are characterized by I-V measurements and impedance spectroscopy. The mobile species create an additional polarization mechanism that can be influenced by an appropriate DC bias. At low biases the dipoles are moveable in the oxide, so they can change their direction by an applied alternating field. At high biases the dipoles are pinned in one direction and the impedance spectrum of the device corresponds to an almost ideal capacitor with no loss mechanisms. Similar to an externally applied DC bias, species from the gas phase that are adsorbed at the electrode-insulator interface can introduce an electric field in the dielectric thin film influencing the mobility of the species. Thus, the contribution of the polarization mechanism to the impedance depends on the gas atmosphere and the change of its real or imaginary part can be used as sensor signal. Additionally, with this new gas sensor structure one can achieve selectivity for reducing and oxidizing gases by choosing appropriate operating points set by a DC bias.

Pages: 122 to 127

Copyright: Copyright (c) IARIA, 2013

Publication date: August 25, 2013

Published in: conference

ISSN: 2308-3514

ISBN: 978-1-61208-297-4

Location: Barcelona, Spain

Dates: from August 25, 2013 to August 31, 2013