In Situ Modification Of The NO/sub x/ And CO Sensitivity Of Thin Pt-gate MOSFET's

Thin discontinuous catalytic metal gate field effect (MOS) devices are known as sensors for hydrogen and hydrogen containing gases like ammonia, ethanol, hydrogen sulfide etc. In this communication we demonstrate the possibility to modify the properties of thin Pt- gates by gas exposure. After a pulse of ammonia the sensors show an increased sensitivity to NO/sub x/. The threshold voltage shift induced by NO/sub x/ is opposite to the direction before the ammonia pulse. A fresh Pt-gate MOS structure showed an eight fold increase of the response to CO gas in 20% oxygen in argon after a ten minute exposure to CO in argon.