Hydrogen sensing in vacuum systems with catalytic field plate MNOS capacitors

The rate of response of catalytic field plate MNOS capacitors to steps in hydrogen partial pressure in a ultra high vacuum UHV.system is reported. The steps in pressure are provided by a gas pulse valve that allows sub-second increases in the pressure. A combination of light sputter cleaning and elevated sensor temperature produces a sensor response fast enough to be of interest in the monitoring of hydrogen partial pressures in a processing chamber