Semiconductor Device-Based Sensors for Gas, Chemical, and Biomedical Applications

Bioaffinity Sensors Based on MOS Field-Effect Transistors 235

© 2011 by Taylor & Francis Group, LLC

electrode would lead to large signals. Some devices had bare silicon surfaces, or surfaces covered

only with native oxide, and in these devices it is possible that hybridization modies traps at the

silicon surface, changing the threshold voltage, or that charge transfer to the silicon occurs through

a mechanism called the Cooperative Molecular Field Effect [57]. But there does not seem to be a

consistent explanation for all the reports of high sensitivity.

Another mystery is the signal observed in devices with suspended gates [58]. These are devices

where polysilicon is coated with nitride and suspended over a FET that is also coated with nitr ...