Kelvin Probe Studies on Sensor Response Characteristics of H2 with PT Metal at PPM Level Concentrations under Non-Zero Humidity Conditions

Authors

  • G. Eranna
  • R. Paris
  • T. Doll

Abstract

In the present study, Kelvin Probe (KP) technique is used to measure the shift in metal work function (WF) of a thin Pt film, deposited on thermally oxidized silicon substrate, on exposure to diluted hydrogen gas.  The WF shift is measured at different H2 concentrations in synthetic air and its sensing behavior is studied for MOSFET configuration.  A fixed flow of 100 sccm of the test gas is maintained for all the measurements.  The 20% of diluted gas is flown through a water bubbler to obtain the required humidity in the test gas.  The sample temperature is maintained at 30oC in the test chamber.  The response characteristics i.e. changes in WF and its variations with respect to H2 concentration is evaluated by using a suitably modified Hewlett Packard Visual Engineering Environment (HP VEE program), a graphical programming language.  The response characteristics are recorded for ascending and descending orders of hydrogen concentration with a time cycle of 20 min ‘on’ state and 20 min ‘off’ state for each concentration of diluted hydrogen.  An empirical relation is derived from the observed shift in WF with respect to H2 concentration values.  It is observed in the present investigation that the response is almost linear for low concentration values and the WF shift is a reversible phenomenon to a large extent in this range of concentration.  The evaluation of response time (?90) suggests saturation in WF shift of the film at about 500 ppm of H2 concentration.

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Published

2020-02-21

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Articles