DC and radio-frequency transport characteristics of lambda deoxyribonucleic acid molecules

Deoxyribonucleic Acid (DNA) is an interesting molecular material which can be used in nano- and bioelectronic device applications [1, 2]. In the aspect of electrical applications, DNA is used as a template of nanowire fabrication and self-assembled network structures. For the biological applications, the hybridization properties of DNA are utilized in bio-sensors or recognition systems. There are a few studies in the electronics properties of DNA molecules. All the previous studies have been limited to DC transport and studies on high frequency behavior of DNA molecules are very rare. In this paper, we report on both DC and radio-frequency (RF) transport characteristics of lambda DNA molecules. Figure 1 shows a schematic of the RF device. Two Ti/Au metal electrodes with the spacing of 2 μm are fabricated on an Al coplanar waveguide gate. The Al thickness of the coplanar waveguide is 200 nm and the waveguide is covered with a 100 nm SiO₂. The lambda phage DNA is diluted with deionized water to the concentration of 50 ng/μℓ. A 1 μℓ DNA solution is dropped on the electrode and it is blown off with nitrogen gas after l min contact. The average current (I_avg) at a constant source-drain bias (V_SD) is measured when a series of RF pulse with the duty cycle of 50 % is applied on the RF gate. Figure 2 shows the I-V_SD curves at several different DC gate bias (V_G). Nonlinear transport properties are observed and the resistance level is relatively high because of large electrode gap. The resistance decreases as V_G gets more negative (the inset shows the dependence of 7 as a function of V_G at V_SD = 5 V.). This result suggests that the lambda DNA behaves as a p-type semiconductor [2]. Figure 3 shows the RF pulse response of the lambda DNA transistor. It shows I_avg-V _SD when a series of gate voltage pulses are applied. The inset of Fig. 3 is the schematic diagram of the transistor structure. The peak-to-peak voltage of the pulse signal is 1 V and the frequency ranges from 0.3 GHz to 1 GHz. We can see the increase of I_SD as increasing the frequency at large V_SD values. The observed frequency characteristics can be explained by a classical non-adiabatic response of the DNA molecules. Our results, for the first time, demonstrate the transport through DNA molecules in RF regime.