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TT4.02 - New Type of Gas Sensors Based on Polarizable Metal Oxide Thin Films 
April 7, 2015   4:00pm - 4:15pm

A new type of Metal-Insulator-Metal (MIM) gas sensor prepared by commonly used semiconductor processing methods is presented. The capacitive device has an extremely simple structure consisting of PECVD-SiO2 and ALD-Al2O3 as dielectric thin films with a thickness in the order of 10 nm sandwiched between two platinum electrodes. At elevated temperatures above 200�C the dielectric films show a distinct polarization mechanism which is attributed to mobile ions that cause a space charge polarization. The adsorption of gas species at the interface of the Pt top electrode and the metal oxides leads to a change in work function or bias offset and thus, a gas-induced change of the impedance of the MIM-structure, sensitive to less than 3 ppm of hydrogen, for example. Based on electrical characterization of these metal-insulator-metal structures using electrical impedance spectroscopy, capacitance-voltage-, and current-voltage-measurements a model is given to explain this unusual gas sensitive permittivity. In particular, this new type of integrated gas sensors show DC bias depending gas selectivity for reducing and oxidizing gases. Furthermore, this new transducer principle can be adapted easily to other gases by choosing appropriate electrode materials.

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