Recognition of hydrogen and ammonia by modified gate metallization of the suspended-gate FET

Suspended-gate field-effect transistors (SGFETs) are investigated for a possible independent detection of hydrogen and ammonia in synthetic air. The suspended gate is modified by electrochemical deposition in order to obtain Pd and SnO x active layers. For SnO x -coated SGFETs, a sensitivity to NH 3 even at room temperature is observed without any response to H 2 . The Pd system is stable at temperatures above 140°C and sensitive to H 2 as well as NH 3 . The combination of both sensors allows the two gaseous species to be recognized independently.