Chemical Modulation of WF

It is interesting to note that other species which can be catalytically cleaved to yield hydrogen can also be detected by the Pd IGFET. Ammonia, lower hydrocarbons, and hydrogen sulfide have all been found to produce a signal (Lundstrom and Svensson, 1985). 

The general mechanism seems to be the catalytic abstraction of hydrogen from the hydrogen-containing molecules. 

the Pd layer serves multiple purposes its surface catalyzes the dissociation of molecular hydrogen, it selectively forms palladium hydride, and it can be used as the metal gate of the field-effect devices. The scheme in Fig. 6.34 also shows the catalytic reaction involving oxygen. If both oxygen and hydrogen are present, the steady-state response of the Pd IGFET includes the surface-catalyzed oxidation. 

In summary, the solubility of atomic hydrogen in Pd is highly selective, but the catalytic reactions at the surface may interfere with the dissociation process, either by adding or removing //ac s to or from the overall scheme. In that respect, oxygen and hydrogen-producing species are the interferants. 

As important as it is, the hydrogen-palladium system is rather limited in its application. For this reason, other electronic materials that could operate on the same principle have been investigated. Organic semiconductors proved to be most useful in that respect. 

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A general solid-state device which allows utilization of the chemical modulation of WF of any EP layer is shown in Figure 10.5. It is called... 

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