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

本研究的目的是开发一种在两个电探针之间具有 10 nm 间隙的 DNA 电测试仪，并使用 DNA 测试仪对电元件进行研究。为了形成具有良好再现性的如此小的间隙，应该在探针制造过程中实现一种小间隙检测机制。为此，开发了一种窄间隙 DNA 测试仪的新制造方法。为了检测硅蚀刻过程中一对探针之间小间隙的形成，监测流过两个探针的电流。在此蚀刻中，仅将探针结构的尖端浸入 KOH 溶液中，同时在两个探针之间施加交流电源。施加的电流在硅结构的最窄部分局部升温，导致硅局部蚀刻。当形成间隙时，由于电流通路被破坏，电流下降。局部加热由此完成，最终停止蚀刻。使用这种方法，可以制造大约 50 nm 间隙的 DNA 镊子。连续的铝膜沉积将使间隙变小。利用自行研制的DNA测试仪和更宽间隙的DNA测试仪，对DNA束的电性能进行了检测。可重复且明确的结果是湿度依赖性。我们发现 DNA 束的电导率受到湿度的强烈影响。这一结果与其他研究人员报道的文献一致。此外，我们还开发了一种Pd涂层DNA线并测量了其电学特性。该电线的电阻约为 74 欧姆-厘米。即使在真空和非常低的温度（高达 77K）下，也可以观察到 DNA-Pd 线的电流。由于在这种情况下湿度的影响将被消除，因此电流应该在涂覆的钯层中流动。

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.