Gate capacitance in electrochemical transistor of single-walled carbon nanotube

In the electrochemical transistor of a single-walled carbon nanotube, we introduced the fourth terminal, which works as a reference electrode. This enables accurate control of change in gate voltage, i.e., potential difference between the electrolyte and the source electrode, and quantitative analyses of the gate capacitance. We found that the geometrical capacitance, which was ignored in the conventional model, makes a crucial contribution to the device characteristics, comparable to that from the chemical capacitance.