TEM Tomography of Pores with Application to Computational Nanoscale Flows in Nanoporous Silicon Nitride (NPN)

Madejski, Gregory R.; Lucas, Kilean; Pascut, Flavius C.; Webb, Kevin F.; McGrath, James L.

doi:10.3390/membranes8020026

Cited by 7 publications

(2 citation statements)

References 38 publications

(65 reference statements)

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“…For approximately cylindrical pores, t eff ≈ t mem , as shown in Figure e. For hourglass-shaped pores, t eff = 1/3 t mem < t mem fit well to the measured ionic conductance of TEM-drilled SiN x pores. , The hourglass-shaped pore structure, in which t eff = 1/3 t mem < t mem , was confirmed by TEM tomography and is also consistent with measured conductance through TEM-drilled pores. ,− …”

Section: Resultssupporting

confidence: 77%

Lifetime and Stability of Silicon Nitride Nanopores and Nanopore Arrays for Ionic Measurements

et al. 2020

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Nanopores are promising for many applications including DNA sequencing and molecular filtration. Solid-state nanopores are preferable over their biological counterparts for applications requiring durability and operation under a wider range of external parameters, yet few studies have focused on optimizing their robustness. We report the lifetime and durability of pores and porous arrays in 10 to 100 nm-thick, low-stress silicon nitride (SiN x ) membranes. Pores are fabricated using a transmission electron microscope (TEM) and/or electron beam lithography (EBL) and reactive ion etching (RIE), with diameters from 2 to 80 nm. We store them in various electrolyte solutions (KCl, LiCl, MgCl2) and record open pore conductance over months to quantify pore stability. Pore diameters increase with time, and diameter etch rate increases with electrolyte concentration from Δd/Δt ∼ 0.2 to ∼ 3 nm/day for 0.01 to 3 M KCl, respectively. TEM confirms the range of diameter etch rates from ionic measurements. Using electron energy loss spectroscopy (EELS), we observe a N-deficient region around the edges of TEM-drilled pores. Pore expansion is caused by etching of the Si/SiO2 pore walls, which resembles the dissolution of silicon found in minerals such as silica (SiO2) in salty ocean water. The etching process occurs where the membrane was exposed to the electron beam and can result in pore formation. However, coating pores with a conformal 1 nm-thick hafnium oxide layer prevents expansion in 1 M KCl, in stark contrast to bare SiN x pores (∼ 1.7 nm/day). EELS data reveal the atomic composition of bare and HfO2-coated pores.

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Section: Resultssupporting

confidence: 77%

Lifetime and Stability of Silicon Nitride Nanopores and Nanopore Arrays for Ionic Measurements

et al. 2020

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“…Merged pores are usually much longer in one of their dimensions, forming a quasi-elliptic, rather than circular, cross section. Further work on the flow through these fringe geometries was performed by Madejski et al…”

Section: Methodsmentioning

confidence: 99%

Entropic Trapping of DNA with a Nanofiltered Nanopore

Lam

Briggs

Kastritis

et al. 2019

ACS Appl. Nano Mater.

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Elucidating the kinetics of DNA passage through a solid-state nanopore is a fertile field of research, and mechanisms for controlling capture, passage, and trapping of biopolymers are likely to find numerous technological applications. Here we present a nanofiltered nanopore device, which forms an entropic cage for DNA following first passage through the nanopore, trapping the translocated DNA and permitting recapture for subsequent reanalysis and investigation of kinetics of passage under confinement. We characterize the trapping properties of this nanodevice by driving individual DNA polymers into the nanoscale gap separating the nanofilter and the pore, forming an entropic cage similar to a "two pores in series" device, leaving polymers to diffuse in the cage for various time lengths, and attempting to recapture the same molecule. We show that the cage results in effectively permanent trapping when the radius of gyration of the target polymer is significantly larger than the radii of the pores in the nanofilter. We also compare translocation dynamics as a function of translocation direction in order to study the effects of confinement on DNA just prior to translocation, providing further insight into the nanopore translocation process. This nanofiltered nanopore device realizes simple fabrication of a femtoliter nanoreactor in which to study fundamental biophysics and biomolecular reactions on the single-molecule level. The device provides an electrically-permeable single-molecule trap with a higher entropic barrier to escape than previous attempts to fabricate similar structures.

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TEM based applications in solid state nanopores: From fabrication to liquid in-situ bio-imaging

Sajeer

Simran²,

Nukala³

et al. 2022

Micron

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TEM Tomography of Pores with Application to Computational Nanoscale Flows in Nanoporous Silicon Nitride (NPN)

Cited by 7 publications

References 38 publications

Lifetime and Stability of Silicon Nitride Nanopores and Nanopore Arrays for Ionic Measurements

Lifetime and Stability of Silicon Nitride Nanopores and Nanopore Arrays for Ionic Measurements

Entropic Trapping of DNA with a Nanofiltered Nanopore

TEM based applications in solid state nanopores: From fabrication to liquid in-situ bio-imaging

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