Understanding Electrical Conduction and Nanopore Formation During Controlled Breakdown.

Jasper P Fried,Aleksandar P Ivanov,Pedro Miguel Sousa,Binoy Paulose Nadappuram,Dayrl P Briggs,Jacob L Swett,James R Yates,Joshua B Edel,Aleksandra Fedosyuk,Jan A Mol

doi:10.1002/smll.202102543

Abstract

Controlled breakdown has recently emerged as a highly appealing technique to fabricate solid-state nanopores for a wide range of biosensing applications. This technique relies on applying an electric field of approximately 0.4-1 V nm-1 across the membrane to induce a current, and eventually, breakdown of the dielectric. Although previous studies have performed controlled breakdown under a range of different conditions, the mechanism of conduction and breakdown has not been fully explored. Here, electrical conduction and nanopore formation in SiNx membranes during controlled breakdown is studied. It is demonstrated that for Si-rich SiNx , oxidation reactions that occur at the membrane-electrolyte interface limit conduction across the dielectric. However, for stoichiometric Si3 N4 the effect of oxidation reactions becomes relatively small and conduction is predominately limited by charge transport across the dielectric. Several important implications resulting from understanding this process are provided which will aid in further developing controlled breakdown in the coming years, particularly for extending this technique to integrate nanopores with on-chip nanostructures.

Highlights

Nanopore sensors consist of a nanometre sized hole in an insulating membrane that separates two chambers of electrolyte solution
We show that depending on the membrane stoichiometry, electrical conduction is limited by either oxidation reactions that must occur at the membrane-electrolyte interface (Si-rich SiNx), or electron transport across the dielectric
To understand the process of nanopore formation during controlled breakdown (CBD) we have studied conduction and breakdown in SiNx membranes when the voltage is applied via (i) metal electrodes on the membrane surface, (ii) electrolyte solutions, and (iii) a combination of the two

Summary

Introduction

Nanopore sensors consist of a nanometre sized hole in an insulating membrane that separates two chambers of electrolyte solution. Solidstate nanopores were typically fabricated using focused charged particle beams to locally sputter material from the membrane[25,26,27,28] This requires specialised equipment, trained operators, and is a labour intensive process limiting the availability of this technique to the wider research community. A technique called controlled breakdown (CBD) has been developed to fabricate nanopores in solid-state membranes[29,30,31] In this method, an electric field of approximately 0.4-1 V/nm is applied across the membrane via the electrolyte solutions whilst simultaneously measuring the resulting current. Better understanding this process will no doubt aid in continuing the development of CBD as a nanopore fabrication technique, e.g. to fabricate nanopores integrated with on-chip nanostructures or in previously unexplored membrane materials

Methods

Results

Conclusion