Hydrogen detection at high concentrations with stabilised palladium

In order to improve the stability to high hydrogen concentrations, of hybrid suspended gate field effect transistors (HSGFETs) with thin palladium films as sensitive layer, Pd–Ni and Pd–Ag alloys have been produced by co-evaporation techniques in UHV. In this paper, the preparation methods as well as hydrogen response measurements are presented. The observed results show that the Pd–Ni alloy is an appropriate material for hydrogen sensing at concentrations up to 2% H2, even at room temperature. The response to 2% H2 is 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 composition had changed after the test gas exposures.