Fabrication Of Solid-state Nanopores Based On Controlled Dielectric Breakdown And Its Mechanism

By virtue of the high reliability and sensitivity,solid-state nanopores play an important role in the next generation sequencing technology.The research on precision manufacturing of small-scale solid-state nanopores is significative to promote the biological detection technology,reveal the secrets of life and prevent diseases.Controlled dielectric breakdown(CBD)is a new craft which can realize low-cost manufacturing of sub-nanometer solid-state nanopores.This topic based on CBD,explores precision manufacturing crafts of silicon nitride(Si Nx)and graphene nanopores and discovers the mechanism of fabrication.The main contents are as follows:1)Key technologies for solid-state nanopores fabrication.On the basis of CBD,a hardware platform was built using the existing materials and equipment in the laboratory to fabricate solid-state nanopores,and a software platform(control system)based on Labview was designed to judge the breakdown events automatically.Finally,the experimental process and requirements were improved.2)Manufacturing process of Si Nx nanopores and its mechanism.CBD experiments on Si Nx chips which independently designed by laboratory were conducted.DC and pulse voltage were used to explore manufacturing rules,and the productivity of sub-5 nm nanopores was improved to more than 95% by increasing the current sampling frequency.The Si Nx nanopores were characterized with a conductivity method,and successfully used to carry out DNA translocation experiments.Combining experimental data and ab initio molecular dynamics simulation,it is found that Si Nx nanopores originated from the generation and accumulation of intrinsic and extrinsic defects.3)Rapid fabrication of Si Nx nanopore.According to the mechanism of CBD on Si Nx,a rapid manufacturing craft based on oxygen plasma treatment was developed.By introducing surface defects and increasing hydrophilicity,the manufacturing electric field was primely reduced to 0.1 V/nm,and the time to breakdown was shortened by at least two orders of magnitude.From the analysis of the electrical model,it is concluded that the decrease of Si Nx resistance and the increase of Si Nx capacitance after oxygen plasma treatment accelerated the generation of extrinsic defects,which is the fundamental reason for rapid fabrication.Based on the minimum surface energy principle,a heating method for reducing the low-frequency noise of nanopores was proposed,which finally reduced the 1/f noise by about an order of magnitude.4)Manufacturing process of graphene nanopores and its mechanism.Graphene chips were prepared by mechanical exfoliation method and wetting transfer technology.Applying CBD to graphene chips,and the minimum breakdown voltage was only 2 V.A graphene-raman experiment was designed,using a confocal raman spectrometer to monitor the CBD process.The data shows that the appearance of graphene nanopores experienced three stages:stretching,defect generation,stabilization.With the classical molecular dynamics simulation,it is found that the stretching of graphene in the solution environment under an electric field is due to the difference in the mobility of anion and cation,and the direction of the protrusion is consistent with the movement direction of the ion with greater mobility.