A Wide Detection Range Mercury Ion Sensor Using Si MOSFET Having Single-Walled Carbon Nanotubes as a Sensing Layer

This letter investigates the response of a wide detection range mercury ion sensor based on Si MOSFET having a floating-gate (FG) and a control-gate (CG) in horizontal direction. Single-walled carbon nanotubes (SWNTs) are formed between the FG and the CG by using an inkjet-printing method. The interaction between the mercury ions and SWNTs is studied by measuring transient current response (I-t). Conductance change is measured from 1 fM to ~10 μM in saturated transient current region. The measured transient response shows that the drain current (I D) is appreciably changed in pMOSFET sensor and almost not changed in nMOSFET sensor. By analyzing the conductance change of the pMOSFET sensor with the concentration of mercury ions, it is shown that the work-function of SWNTs increases due to hole doping and the I D increases as a result.