Fabrication of memristive devices by using Ni-DNA
DNA is one of the most promising quasi-one-dimensional nanomaterials because of its adjustable length and self-assembly properties. In order to increase the intrinsic conductivity of DNA, DNA is chelated with Ni ions. In this work, the Ti/Au electrodes were deposited and patterned on the substrate by standard electron-beam lithography and thermal evaporation. Moreover, we immobilize Ni-DNA on the gold electrode surface of device by using DNA self-assembled monolayer (SAM) or electrophoretic placement. In these measurements, current flowing through the Ni-DNA was measured when the bias voltage was supplied on the two gold electrodes. I-V curves show obviously a hysteretic loop and a feature of negative differential resistance (NDR) that indicates the emergence of a memristive system. In our previous studies, we verified that the NDR effect is attributed to the redox reaction between Ni2+ and Ni3+ within the DNA base pairs. Ni-DNA nanowires are further used to demonstrate the application of memory devices. The memory device can be set by either positive or negative writing, and it can be read by current at a constant bias voltage across the pair electrodes. In addition, the polarized states remain longer in time under the DC reading in comparison with the AC reading. The multiple state of the Ni-DNA device is possibly attributed to a different ratio between Ni3+ and Ni2+ ions in Ni-DNA nanowires for different writing time. If the writing time and the writing process are precisely controlled, the Ni-DNA memory device can be operated at multiple states.
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