Fabrication And Application Of The Nanopore Sensor For DNA Detection Based On Two-dimensional Materials

Nanopore-based sensing, as the leader of the third generation gene sequencing technology, with advantages of label-free, amplification-free, high-throughput, etc., is the most promising method for rapid and low-cost DNA sequencing. Nanopores are usually classified into two groups:biological nanopores and solid-state nanopores. With the development of semiconductor processing technology, solid-state nanopores are getting more and more attentions. Recently, two-dimensional materials with superior performance have been successfully fabricated in laboratories. How to use two-dimensional materials to fabricate nanopore devices has become a pressing question in Nanopore-based sensing field. In this paper, using graphene and molybdenum disulfide, nanopore devices were fabricated and DNA detection experiments were conducted to research this problem..For graphene material, chemical vapor deposition method was finally chosen to grow graphene for DNA detection devices after compared with other three methods, chemical reduction of graphene oxide, thermal sublimation of Silicon Carbide and mechanical exfoliation. By using copper as substrate and using methane as a carbon source, single layer graphene with large area and high quality was successfully made and was then transferred to the Si3N4/Si substrate prepared for DNA detection. After that, nanopore was made in graphene on silicon nitride substrate by focus ion beam and DNA translocation experiments were conducted. It was found that hydrophilic treatments by plasma could improve the effective diameter of graphene nanopores and reduce the noise of current signals during DNA translocation experiments. Besides, the signals of single-stranded DNA and double-stranded DNA have been separated by graphene nanopore.For molybdenum disulfide material, currently molybdenum disulfide with high quality could only be made by mechanical exfoliation method. So we developed a method which could transfer two-dimensional materials made by mechanical exfoliation method with high precision. Using this method the molybdenum disulfide nanopore devices and even a graphene/molybdenum disulfide heterostructure was successfully fabricated without any damage to the materials and substrates, which proved the feasibility and adaptability of this transfer method. After that, the combination of field effect transistor and nanopore device based on molybdenum disulfide was researched, and then a processing method was proposed to achieve this kind of composite device. Basing on the theory of DNA translocation, semi-finished products which are same as finished products in blockage analysis were made to conduct the DNA Translocation experiments. Finally it was found that this kind of device offers high signal to noise ratio and is stable in electrolyte environment during the DNA translocation experiments.