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 themercury ions and SWNTs is studied by measuring transient current response ( I–t ). Conductance change is measured from 1 fM to $\sim 10~\mu \text{M}$ in saturated transient current region. The measured transient response shows that the drain current ( ${I}_{{D}}$ ) is appreciably changed in p MOSFET sensor and almost notchanged in n MOSFET sensor. By analyzing the conductance change of the p MOSFET 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.