
102 Semiconductor Device-Based Sensors for Gas, Chemical, and Biomedical Applications
© 2011 by Taylor & Francis Group, LLC
For further study, devices were tested under both forward and reverse bias conditions at room
temperature (25°C) in a nitrogen atmosphere at hydrogen concentrations ranging from 0 to 500 ppm,
controlled by diluting the gas mix with nitrogen using mass ow controllers. There was again an
increase in current under both forward and reverse bias conditions upon exposure to hydrogen, as
shown in Figure3.5. This result is consistent with previously discussed mechanisms [60,61]. The
hydrogen atoms form a dipole layer, loweri