Journal
ACS SENSORS
Volume 2, Issue 2, Pages 300-307Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acssensors.6b00826
Keywords
flicker noise; nanopore; electrical double layer; model; power spectrum density; low frequency range; Hooge's theory
Funding
- Swedish Research Council [621-2014-6300]
- Stiftelsen Olle Engkvist Byggmastare [2016/39]
- Wallenberg Academy Fellow Program
- Swedish Strategic Research Foundation
- Finnish Centre of Excellence on Nuclear and Accelerator Based Physics by the Academy of Finland [251353]
- China Scholarship Council
- Academy of Finland (AKA) [251353] Funding Source: Academy of Finland (AKA)
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Nanopore technology has been extensively investigated for analysis of biomolecules, and a success story in this field concerns DNA sequencing using a nanopore chip featuring an array of hundreds of biological nanopores (BioNs). Solid-state nanopores (SSNs) have been explored to attain longer lifetime and higher integration density than what BioNs can offer, but SSNs are generally considered to generate higher noise whose origin remains to be confirmed. Here, we systematically study low frequency (including thermal and flicker) noise characteristics of SSNs measuring 7 to 200 nm in diameter drilled through a 20-nmthick SiNs membrane by focused ion milling. Both bulk and surface ionic currents in the nanopore are found to contribute to the flicker noise, with their respective contributions determined by salt concentration and pH in electrolytes as well as bias conditions. Increasing salt concentration at constant pH and voltage bias leads to increase in the bulk ionic current and noise therefrom. Changing pH at constant salt concentration and current bias results in variation of surface charge density, and hence alteration of surface ionic current and noise. In addition, the noise from Ag/AgCI electrodes can become predominant when the pore size is large and/or the salt concentration is high. Analysis of our comprehensive experimental results leads to the establishment of a generalized nanopore noise model. The model not only gives an excellent account of the experimental observations, but can also be used for evaluation of various noise components in much smaller nanopores currently not experimentally available.
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