Effects of gate voltage on the current-voltage characteristics of λ-DNA molecules

We investigated the effects of gate voltage on the source-drain current (Id) measured through a bundle of A-phase DNA molecular wires. The DNA molecules were attached on gold electrodes with a nanometer gap (similar to 20 nm), and I-ds was measured by changing both gate and source-drain voltages. We found that the modulation Of Id was possible by simply controlling the magnitude and/or polarity of gate voltage. For example, the absolute value of I-ds increases when the magnitude of gate voltage increases toward the positive direction. On the other hand, the absolute value of I-ds decreases if the magnitude of negative gate voltage increases. Based on these results, we argued that the A-phase DNA molecules might be treated as n-type semiconductor materials. We also suggested that the effective diameter of DNA wires is an important factor in deciding the magnitude of conductivity.