Abstract
Graphene-based nanopore devices have shown tantalizing potential in single molecule detection for their monoatomic membrane thickness which is roughly equal to the gap between nucleobases. However, high noise level hampers applications of graphene nanopore sensors, especially at low frequencies. In this article, we report on a study of the contribution of suspended graphene area to noise level in full frequency band. Monolayer graphene films are transferred onto SiNx substrates preset with holes in varied diameters and formed self-supported films. After that, the films are perforated with smaller, nanoscale holes. Experimental studies indicate a dependency of low-frequency 1/f noise on the underlying SiNx geometry. The contribution of the suspended graphene area to capacitance which affects the noise level in the high frequency range reveals that the graphene free-standing film area influences noise level over a wide frequency region. In addition, the low-frequency noise demonstrates a weak dependency on salt concentration, in deviation from Hooge’s relation. These findings and attendant analysis provide a systematic understanding of the noise characteristics and can serve as a guide to designing free-standing monolayer graphene nanopore devices.
Highlights
Solid-state nanopores are uniquely suited for single molecule detection due to their superior attributes over biological nanopores that allow long service period, specific design towards concerted detection target and compatibility with devices [1,2,3]
We have provided an elaborate description and detailed analysis about the impact caused by the suspended area of monolayer graphene film to noise characteristic in a nanopore system
That low-frequency 1/f noise should scale with resistance according to Hooge’s relation with a power law of A ∼ R3 is in discrepancy from our experimental observation of A ∼ R1.33±0.80
Summary
Solid-state nanopores are uniquely suited for single molecule detection due to their superior attributes over biological nanopores that allow long service period, specific design towards concerted detection target and compatibility with devices [1,2,3]. Different from conventional long-channel nanopores, graphene is one of the typical 2D materials whose layer thickness is 0.34 nm, to the extent that its sub-nanometer scale approaches the interval between two contiguous bases in a single DNA molecule. Compared to commonly insulated membrane materials used for nanopore sensor fabrication such as silicon nitride (SiNx) [4], aluminum oxide (Al2O3) [5], and silicon oxide (SiO2) [6], graphene has good electronic conductivity and robust mechanical properties. Despite these superiorities, high noise levels impede the applications of graphene nanopore sensors. The original expectation of single-nucleobase resolution will be sacrificed as the result of any thickness increase during the modification process
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