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Current–voltage characteristics of the break-junction before and after the formation of the nanogap. On average, current at 0.5 V dropped from to less than 0.3 nA after nanogap formation. Devices with leakage current less than 1 nA were considered to be candidate devices for DNA docking. Inset (a) shows SEM images of the break-junction structure before electromigration, and inset (b) shows the sketch and FESEM image of one of the structures where nanogap was formed.
(a) Comparison of current–voltage characteristics of conduction through bare nanogaps, with DNA docked in it for Sequences 1 and 3, and for the control chip after incubation in nonthiolated Sequence 1, where no conduction was observed. (b) Two representative plots for Sequence 1 show decrease in conduction after temperature cycling. Conduction was restored after reincubation and temperature cycling step.
Current–voltage plots of the three DNA sequences. Close to 0 voltage, the resistance decreases with increasing GC content. The resistivity values assume a single molecule, 6.7 nm long and 2 nm in diameter. Inset shows a number of plots for Sequences 1 and 3, all measured on different devices.
The three 18-mer DNA sequences and their melting temperatures, used in our experiments.
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