Abstract

Ultra-thin solid-state nanopore with good wetting property is strongly desired to achieve high spatial resolution for DNA sequencing applications. Atomic thick hexagonal boron nitride (h-BN) layer provides a promising two-dimensional material for fabricating solid-state nanopores. Due to its good oxidation resistance, the hydrophilicity of h-BN nanopore device can be significantly improved by UV-Ozone treatment. The contact angle of a KCl-TE droplet on h-BN layer can be reduced from 57° to 26° after the treatment. Abundant DNA translocation events have been observed in such devices, and strong DNA-nanopore interaction has been revealed in pores smaller than 10 nm in diameter. The 1/f noise level is closely related to the area of suspended h-BN layer, and it is significantly reduced in smaller supporting window. The demonstrated performance in h-BN nanopore paves the way towards base discrimination in a single DNA molecule.

Introduction

As one of the most promising concepts, DNA sequencing with nanopore has attracted a lot of attention since 19961. DNA translocation1,2,3 and base discrimination4 has been demonstrated in biological nanopores made of specific proteins. Solid-state nanopores, however, are strongly preferred for higher stability and easier device integration. The first solid-state nanopores are fabricated in silicon nitride (Si3N4) membranes that are tens of nanometers thick5, and significant progress has been made in detection of DNA translocation6,7, and DNA motion control8 in such nanopore devices. To achieve base discrimination in a single DNA molecule, the effective thickness of a solid-state nanopore has to be reduced down to sub-nanometer. For such propose, atomic thick graphene layers has been employed in fabricating nanopore devices featured with high resolution and geometrical sensitivity9,10,11,12. On the other hand, the hydrophilicity of nanopore is practically important to avoid clogging due to strong nonspecific hydrophobic interaction with DNA. Recently, the hydrophilicity of graphene nanopores has been improved by atomic-layer deposition of titanium dioxide11 and self-assembled hydrophilic coating13, which however increases the effective thickness of the pores. New types of atomic thick nanopores with high hydrophilicity are thus still strongly desired.