Development of a 10 nm gap DNA electric tester and investigation of electric elements based on DNA molecules

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The aim of this study is to develop a DNA electric tester having a 10 nm gap between two electric probes and investigation of electric elements using DNA testers. To form such a small gap with good reproducibility, a kind of the small-gap detection mechanism should be implemented for probe fabrication process. For this purpose, a new fabrication method of a narrow gap DNA tester has been developed. In order to detect the formation of a small gap between a pair of probes during silicon etching, current flow though the two probes was monitored. In this etching, only the tips of the probe structure are dipped into a KOH solution while AC power is applied between the two probes. The applying current heat up at the narrowest part of the silicon structure locally, resulting in silicon etching locally. When a gap is formed, the current is dropped since the current pass is broken. The local heating will hence finished, eventually stopping the etching. Using this method, approximately 50 nm gap DNA tweezers could be fabricated. Successive Al film deposition will make the gap smaller.Using the developed DNA testers and more wider gap DNA testers, electrical properties of DNA bundle were examined. The reproducible and explicit result is humidity dependency. We found that electrical conductance of DNA bundles is strongly affected by humidity. This result is consistent with literatures reported by other researchers.Furthermore, we have developed a Pd coated DNA wire and measured its electrical characteristics. The wire showed the electrical resistively of approximately 74 ohm-cm. Even in vacuum and at very low temperature (up to 77K), the current flow was observed for the DNA-Pd wire. Since the effect of humidity will be eliminated in this case, the current flow was supposed to be in the coated Pd layer.