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Fabrication of 3-nm-thick Si3N4 membranes for solid-state nanopores using the poly-Si sacrificial layer process.

Yanagi I, Ishida T, Fujisaki K, Takeda K - Sci Rep (2015)

Bottom Line: However, until now, stable wafer-scale fabrication of Si3N4 membranes with a thickness of less than 5 nm has not been reported, although a further reduction in thickness is desired to improve spatial resolution.Based on the relationship between the ionic current through the nanopores and their diameter, the effective thickness of the nanopores was estimated to range from 0.6 to 2.2 nm.Moreover, DNA translocation through the nanopores was observed.

View Article: PubMed Central - PubMed

Affiliation: Hitachi Ltd., Central Research Laboratory, 1-280 Higashi-koigakubo, Kokubunji, Tokyo, 185-8603.

ABSTRACT
To improve the spatial resolution of solid-state nanopores, thinning the membrane is a very important issue. The most commonly used membrane material for solid-state nanopores is silicon nitride (Si3N4). However, until now, stable wafer-scale fabrication of Si3N4 membranes with a thickness of less than 5 nm has not been reported, although a further reduction in thickness is desired to improve spatial resolution. In the present study, to fabricate thinner Si3N4 membranes with a thickness of less than 5 nm in a wafer, a new fabrication process that employs a polycrystalline-Si (poly-Si) sacrificial layer was developed. This process enables the stable fabrication of Si3N4 membranes with thicknesses of 3 nm. Nanopores were fabricated in the membrane using a transmission electron microscope (TEM) beam. Based on the relationship between the ionic current through the nanopores and their diameter, the effective thickness of the nanopores was estimated to range from 0.6 to 2.2 nm. Moreover, DNA translocation through the nanopores was observed.

No MeSH data available.


Related in: MedlinePlus

Long-term continuous measurement of current through nanopores.(a) Continuous measurement of current through a nanopore at 0.1 V for one hour. Both cis and trans chambers were filled with 1 M KCl buffer solution. dsDNA was not applied. (b) Continuous measurement of current through a nanopore at 0.1 V for half an hour. The cis chamber was filled with 1 M KCl buffer solution with 20 nM 1 kbps dsDNA. The trans chamber was filled with 1 M KCl buffer solution. (c) Changes in baseline conductance (G0) with time. (d) Changes in G0 from the initial baseline conductance (G0ini). The current was plotted every 3 minutes.
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f7: Long-term continuous measurement of current through nanopores.(a) Continuous measurement of current through a nanopore at 0.1 V for one hour. Both cis and trans chambers were filled with 1 M KCl buffer solution. dsDNA was not applied. (b) Continuous measurement of current through a nanopore at 0.1 V for half an hour. The cis chamber was filled with 1 M KCl buffer solution with 20 nM 1 kbps dsDNA. The trans chamber was filled with 1 M KCl buffer solution. (c) Changes in baseline conductance (G0) with time. (d) Changes in G0 from the initial baseline conductance (G0ini). The current was plotted every 3 minutes.

Mentions: Long-term continuous measurements of Icis-trans through the nanopores at 0.1 V are shown in Fig. 7. Figure 7a shows Icis-trans thorough a nanopore with a ϕm of 3.36 nm without applying DNA into the cis chamber. Figure 7b shows Icis-trans thorough a nanopore with a ϕm of 3.65 nm after adding 20 nM 1 kbps double-stranded DNA (dsDNA) into the cis chamber. Typical Icis-trans noise power spectrums are shown in Supplementary Section SI-3. After adding dsDNA into the cis chamber, ionic current blockades were frequently observed, which indicated the occurrence of dsDNA translocation through the nanopores. However, the baseline Icis-trans current increased over time, which indicated widening of the nanopores. TEM images of the nanopores before and after the measurement of Icis-trans are shown in Supplementary Section SI-4. The widening of the nanopores was confirmed after the measurements. Such widening of nanopores after ionic-current measurements has been reported previously27. This increase in current was not observed prior to fabrication of the nanopores (inset of Fig. 5). Therefore, it is assumed that areas of the membrane near the edges of nanopores are weaker than the other areas. Figure 7c shows the change in baseline conductance (G0) with time, and Fig. 7d shows the change in G0 from the initial baseline current (G0ini) that was measured at the beginning of the measurement period. Unfilled/filled symbols represent the data obtained from measurements with/without dsDNA in the cis chamber. The increase in G0 was approximately 5 nS for a half hour at 0.1 V.


Fabrication of 3-nm-thick Si3N4 membranes for solid-state nanopores using the poly-Si sacrificial layer process.

Yanagi I, Ishida T, Fujisaki K, Takeda K - Sci Rep (2015)

Long-term continuous measurement of current through nanopores.(a) Continuous measurement of current through a nanopore at 0.1 V for one hour. Both cis and trans chambers were filled with 1 M KCl buffer solution. dsDNA was not applied. (b) Continuous measurement of current through a nanopore at 0.1 V for half an hour. The cis chamber was filled with 1 M KCl buffer solution with 20 nM 1 kbps dsDNA. The trans chamber was filled with 1 M KCl buffer solution. (c) Changes in baseline conductance (G0) with time. (d) Changes in G0 from the initial baseline conductance (G0ini). The current was plotted every 3 minutes.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4589763&req=5

f7: Long-term continuous measurement of current through nanopores.(a) Continuous measurement of current through a nanopore at 0.1 V for one hour. Both cis and trans chambers were filled with 1 M KCl buffer solution. dsDNA was not applied. (b) Continuous measurement of current through a nanopore at 0.1 V for half an hour. The cis chamber was filled with 1 M KCl buffer solution with 20 nM 1 kbps dsDNA. The trans chamber was filled with 1 M KCl buffer solution. (c) Changes in baseline conductance (G0) with time. (d) Changes in G0 from the initial baseline conductance (G0ini). The current was plotted every 3 minutes.
Mentions: Long-term continuous measurements of Icis-trans through the nanopores at 0.1 V are shown in Fig. 7. Figure 7a shows Icis-trans thorough a nanopore with a ϕm of 3.36 nm without applying DNA into the cis chamber. Figure 7b shows Icis-trans thorough a nanopore with a ϕm of 3.65 nm after adding 20 nM 1 kbps double-stranded DNA (dsDNA) into the cis chamber. Typical Icis-trans noise power spectrums are shown in Supplementary Section SI-3. After adding dsDNA into the cis chamber, ionic current blockades were frequently observed, which indicated the occurrence of dsDNA translocation through the nanopores. However, the baseline Icis-trans current increased over time, which indicated widening of the nanopores. TEM images of the nanopores before and after the measurement of Icis-trans are shown in Supplementary Section SI-4. The widening of the nanopores was confirmed after the measurements. Such widening of nanopores after ionic-current measurements has been reported previously27. This increase in current was not observed prior to fabrication of the nanopores (inset of Fig. 5). Therefore, it is assumed that areas of the membrane near the edges of nanopores are weaker than the other areas. Figure 7c shows the change in baseline conductance (G0) with time, and Fig. 7d shows the change in G0 from the initial baseline current (G0ini) that was measured at the beginning of the measurement period. Unfilled/filled symbols represent the data obtained from measurements with/without dsDNA in the cis chamber. The increase in G0 was approximately 5 nS for a half hour at 0.1 V.

Bottom Line: However, until now, stable wafer-scale fabrication of Si3N4 membranes with a thickness of less than 5 nm has not been reported, although a further reduction in thickness is desired to improve spatial resolution.Based on the relationship between the ionic current through the nanopores and their diameter, the effective thickness of the nanopores was estimated to range from 0.6 to 2.2 nm.Moreover, DNA translocation through the nanopores was observed.

View Article: PubMed Central - PubMed

Affiliation: Hitachi Ltd., Central Research Laboratory, 1-280 Higashi-koigakubo, Kokubunji, Tokyo, 185-8603.

ABSTRACT
To improve the spatial resolution of solid-state nanopores, thinning the membrane is a very important issue. The most commonly used membrane material for solid-state nanopores is silicon nitride (Si3N4). However, until now, stable wafer-scale fabrication of Si3N4 membranes with a thickness of less than 5 nm has not been reported, although a further reduction in thickness is desired to improve spatial resolution. In the present study, to fabricate thinner Si3N4 membranes with a thickness of less than 5 nm in a wafer, a new fabrication process that employs a polycrystalline-Si (poly-Si) sacrificial layer was developed. This process enables the stable fabrication of Si3N4 membranes with thicknesses of 3 nm. Nanopores were fabricated in the membrane using a transmission electron microscope (TEM) beam. Based on the relationship between the ionic current through the nanopores and their diameter, the effective thickness of the nanopores was estimated to range from 0.6 to 2.2 nm. Moreover, DNA translocation through the nanopores was observed.

No MeSH data available.


Related in: MedlinePlus