Development of a Oxygen Sensor for Marine ... - DTU Nanotech

2.3. SUMMARY 11
of oxygen molecules, which is similar to that of a Clark sensor (more about
this in Chapter 3). However the way the ISFET detects it, is by determining
the surface potential at the insulator/electrolyte interface.[19] Also in
the case of the pH-ISFET the surface of the gate oxide will contain OH −
molecules, which can be protonated and deprotonated, so when the gate oxide
contacts an aqueous solution, the change in pH will cause the silicon
surface potential to change as well.
The advantages of the ISFET is that the CMOS and MOSFET are tried
and used technologies. However chemical sensors are still a relative new area
for this to be used in, and as such suffers from ’child’-diseases.
Disadvantages have included light sensitivity, lack of solid-state reference
electrodes, and packaging integrity difficulties. [20]
2.3 Summary
While both the Optodes and the ISFET are viable ways of creating a oxygen
sensor, both had certain distinct disadvantages that made the Clark type a
better choice. However of the two, the optodes might in the future become a
superior solution, once the problems with size and power supply have been
solved.