Abstract
We propose a novel technique to investigate the gas sensitivity of materials for implementation in field-effect transistor-based gas sensors. Our technique is based on the measurement of the surface charge induced by gas species adsorption, using an electrometer. Platinum sensitivity to hydrogen diluted in synthetic air has been evaluated with the proposed charge measurement technique in the operation temperature range from 80 to 190 °C at constant H2 concentration of 4 % and for different concentrations ranging from 0.5 to 4 % at 130 °C.
Highlights
We propose a novel technique to investigate the gas sensitivity of materials for implementation in field-effect transistor-based gas sensors
If the inner surface of field-effect transistor (FET) gate is accessible to gas species, the induced voltage shift associated to the work function variation acts as an artificial voltage which is added to an externally applied gate voltage and affects the conductance of the transistor channel [1, 2]. This has been achieved by either a permeable gate electrode made of catalytic metals, in so-called Lundstrom Metal oxide semiconductor field-effect transistor (MOSFET), or a suspended gate with a sensitive layer deposited on the outer surface, in suspended gate-FET (SG-FET)-based gas sensors [1, 2]
Since adsorbed species are in a dynamic equilibrium with the gas phase [3, 4], and since the voltage shift is proportional to the number of adsorbed gas species per surface unit, work function variation measurements can be used to monitor the gas concentration
Summary
We propose a novel technique to investigate the gas sensitivity of materials for implementation in field-effect transistor-based gas sensors. Platinum sensitivity to hydrogen diluted in synthetic air has been evaluated with the proposed charge measurement technique in the operation temperature range from 80 to 190 °C at constant H2 concentration of 4 % and for different concentrations ranging from 0.5 to 4 % at 130 °C. This has been achieved by either a permeable gate electrode made of catalytic metals, in so-called Lundstrom MOSFETs (catalytic MOSFETs), or a suspended gate with a sensitive layer deposited on the outer surface, in suspended gate-FET (SG-FET)-based gas sensors [1, 2]. SG-FET-based gas sensors have been demonstrated to detect a broad range of gases [1, 2] such as CO [9, 10] and H2 [1, 11], thanks to real flexibility in sensitive layer choice and integration, and operate at room temperature or slightly above
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