Hydrogen detection at high concentrations with stabilised palladium

In order to improve the stability to high hydrogen concentrations, of hybri d suspended gate field effect transistors (HSGFETs) with thin palladium fil ms as sensitive layer, Pd-Ni and Pd-Ag alloys have been produced by co-evap oration techniques in UHV. In this paper, the preparation methods as well a s hydrogen response measurements are presented. The observed results show t hat the Pd-Ni alloy is an appropriate material for hydrogen sensing at conc entrations up to 2% H-2, even at room temperature. The response to 2% H-2 i s around 500 mV at dry conditions. It is reduced to less than half of this value with moistened carrier gas, but at the same time, the desorption time is lowered. In contrast, the Pd-Ag alloy was not stable. A large drift of the sensor signal was observed and the morphology as well as the compositio n had changed after the test gas exposures. (C) 2001 Published by Elsevier Science B.V.