Electrical Behavior of Nano-scale Junctions with Well Engineered Double Stranded DNA Molecules

The electrical conduction through polycation stabilized short (15 base-pairs, ~5.4nm) double standard (ds)-DNA molecules are measured at ambient. The metal-DNA interface properties are studied by functionalizing the DNA with a thiol group attachment at their 3’ and 5’ ends using different spacers. The thermodynamically stable ds-DNA strands are prepared from the single DNA chains and their complements in a phosphate buffer solution (PBS) and immobilized between isolated pairs of gold (Au) electrodes. Molecular scale gaps between contacts were formed by an electromigration technique performed on a lithographically defined Au micro-wire that is e-beam evaporated over oxidized silicon substrate using a molecular adhesion monolayer. The DNA strands are stabilized by exposing to a polycation environment (spermidine in PBS). In the 15 base-pair double strands, the conductivity is observed to change systematically with DNA sequence and end-group structure.