Adsorption induced gas transport phenomena in narrow air channels recorded with work function detectors

Gas transport in narrow air channels (length-to-height ratio 1 mm/1 degrees mu m) is characterized by work function detectors like hybrid suspended gate field effect transistors (HSGFETs) with sensitive areas located in the middle of the channel. A thin platinum layer covered one side of the channel. In order to separate the influence of the size of the channel structure on the gas exchange Kelvin probe measurements with platinum coated reference electrodes were carried out simultaneously. For the HSGFET we have observed time lags and suppressions of reactions, which indicate a strong adsorption dependence of gas exchange for the investigated testing gas mixture of hydrogen in nitrogen or synthetic air, respectively The results are discussed in relation to common models for the flow in thin capillaries. We also point out the special features of narrow air channels for investigating adsorption related phenomena and for improving chemical sensor characteristics by incorporating them into small air gaps. (C) 1996 American Vacuum Society.