Single molecule DNA device measured with triple-probe atomic force microscope

We have measured the electric properties of a three-terminal single molecule DNA device with a triple-probe atomic force microscope (T-AFM). The T-AFM permits us to connect a single DNA molecule with carbon nanotube (CNT) electrodes as source, drain, and gate terminals. As the gate bias voltage is increased, the voltage gap region decreased in the current–voltage $\mathrm{(I–V)}$ curves. Furthermore, we can observe the clear steps in the $\mathrm{I–V}$ curve at crossing the DNA molecule and the CNT-gate electrode with gate biased.