A Generalized noise study of solid-state nanopores at low frequencies

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1 Supporting Information A Generalized noise study of solid-state nanopores at low frequencies Chenyu Wen, 1, Shuangshuang Zeng, 1, Kai Arstila, 2 Timo Sajavaara, 2 Yu Zhu 3, Zhen Zhang, 1, * and Shi-Li Zhang 1 1. Division of Solid-State Electronics, Department of Engineering Sciences, Uppsala University, SE Uppsala, Sweden 2. Department of Physics, University of Jyväskylä, P.O. Box 35, FI-40014, Finland 3. IBM T J Watson Research Center, 1101 Kitchawan Rd, Yorktown Heights, NY 10598, USA The authors contributed equally to this work. * To whom correspondence should be addressed: zhen.zhang@angstrom.uu.se Table of Contents Figure S1 Measurement setup and schematic cross-section of the nanopore device structure Figure S2 Noise PSDs of the Ag/AgCl electrodes in salt solutions of different KCl concentrations Figure S3 Comparison of noise PSD from the Ag/AgCl electrodes in 10 mm, 100 mm and 1 M KCl salt solutions Figure S4 Comparison of noise PSD from the Ag/AgCl electrodes in series with a resistor of 100 kω, 1 MΩ, and 10 MΩ Figure S5 Equivalence of two equivalent circuits of noise in the nanopore system Figure S6 Low-frequency noise characteristics of a 7.2 nm nanopore Figure S7 Variation of surface charge density on SiN x surface with KCl concentration Figure S8 Noise PSD of nanopores of different diameters measured in 0.1 mm KCl solution with ph ranging from 2.5 to 11 Figure S9 Contribution map for all noise components in the LF range Figure S10 Variation of the noise RMS with KCl concentration and current bias for nanopores Table S1 Parameters used in the model fitting in Figure 5 in main text S-1

2 Measurement setup and nanopore device Supporting Figure S1. Measurement setup and schematic cross-section of the nanopore device structure. S-2

3 Properties of the 1/f-shape noise from the Ag/AgCl electrodes In order to clarify the noise behavior from the Ag/AgCl electrodes, we measured the current noise from them separately. To carry out this measurement, the nanopore chip was replaced with a 1 MΩ resistor making the setup with two lids each with its own Ag/AgCl electrode sandwiching a KCl solution to complete the loop. Lying outside the KCl solution, this resistor imitated the resistance generated by the nanopore. The resistor only generated white thermal noise. The noise PSDs measured with the salt solutions of 10 mm, 100 mm, and 1 M KCl concentration are shown in Supporting Figure S2a-c, respectively. The white thermal noise level from the 1 MΩ resistor is marked as a black horizontal dash line in each figure. Supporting Figure S2. Noise PSDs of the Ag/AgCl electrodes in salt solutions of different KCl concentrations. (a-c) Noise PSDs under different current biases ranging from 10 to 100 na in 10 mm, 100 mm and 1 M KCl, respectively. (d) Comparison of noise PSDs in these three KCl concentrations at 20 na current bias. From the noise PSD of Ag/AgCl, it is clear that the current dependence of noise is negligible. Hence, it is not flicker noise but rather a 1/f-shape PSD that is at work and it is attributed to the Ag/AgCl electrodes. Supporting Figure S1d compares the noise PSD obtained with different KCl concentrations, and it only shows a weak dependence on KCl concentration. Similar observations were also made when the series resistor was changed to 100 kω and 10 MΩ, see Supporting Figure S3. According to the analysis and conclusions in [1], this noise from the electrodes is generated by the thermal noise associated S-3

4 with the ionic solution resistance of the nanopore modulated by the non-flatband frequency response of the electrode-solution interface. Supporting Figure S3. Comparison of noise PSD from the Ag/AgCl electrodes in 10 mm, 100 mm and 1 M KCl salt solutions. Resistor connected to the measurement setup: (a) 100 kω and (b) 10 MΩ. Bias current: 20 na. Supporting Figure S4. Comparison of noise PSD from the Ag/AgCl electrodes in series with a resistor of 100 kω, 1 MΩ, and 10 MΩ. KCl concentration: (a) 10 mm, (b) 100 mm, and (c) 1 M. Bias current: 20 na. S-4

5 A clear trend is seen in Supporting Figure S4, a lower noise level is generated when a larger resistor was connected to the Ag/AgCl electrodes. This behavior persists with salt solutions of 10 mm, 100 mm, and 1 M KCl concentrations. Hence, the Ag/AgCl electrodes work as a voltage source and induce current fluctuations on the resistance of nanopore. As shown in the left panel of Supporting Figure S5, S v represents the voltage noise source from the Ag/AgCl electrodes and S I is the flicker current noise generated by the nanopore itself. R is the total resistance of the system, mainly determined by the nanopore. In the current noise measurement shown in the right panel, the effect of S v is equivalent to a current noise source S I with an intensity of S v/r 2 that in its turn is connected in parallel with S I. Thus, the total noise intensity is the sum of S I and S I. Supporting Figure S5. Equivalence of two equivalent circuits of noise in the nanopore system. This voltage source of noise has certain intensity independent of current and KCl concentration. the impedance decreases by 10 times, the current noise PSD will increase by 100 times. If S-5

6 Noise characteristics of the 7.2 nm nanopore Supporting Figure S6. Low-frequency noise characteristics of a 7.2 nm nanopore. (a) Noise PSD in 1 M KCl concentration under various current biases. (b) Noise RMS values compared with those of other size nanopores. S-6

7 Calculation of surface charge density Supporting Figure S7. Variation of surface charge density on SiN x surface with KCl concentration at ph=5, calculated according to the site binding model. Other parameters used: 4 density of surface silanol N s=3x10 18 [1/m 2 ] and density of primary amine sites N nit=2x10 18 [1/m 2 ]; dissociation constants k a=15.8 [M], k b=6.31x10-8 [M], and k n=1x10-10 [M]; Stern layer capacitance C st=0.2 [F/m 2 ]. S-7

8 Noise characteristics for differently sized nanopores Supporting Figure S8. Noise PSD of nanopores of different diameters measured in 0.1 mm KCl solution with ph ranging from 2.5 to 11. Diameter of the nanopore: (a) 40 nm, (b) 65 nm, (c) 96 nm, and (d) 192 nm. The curled arrows help show how the noise levels first increase and then decrease with increasing ph value. S-8

9 Contribution map for all noise components in the LF range. Supporting Figure S9. Contribution map for all noise components in the LF range. Variation of the squared noise RMS corresponding to the surface current, bulk current, Ag/AgCl electrodes, and pore resistance (thermal) with, (a-c) KCl concentration at current bias of 10 na, 50 na, and 100 na, respectively, and (d-f) current bias in KCl solution of 1 mm, 10 mm, and 100 mm concentration, respectively. Supporting Figure S9 shows the various noise contributions in terms of squared RMS in the 0.1 Hz-1 khz frequency range as well as their dependencies on KCl concentration and current bias for 20 nm diameter nanopores drilled in 20 nm thick membranes for an illustration relevant to the experimental settings in this work. The green, magenta, blue, and orange areas represent, respectively, the noise contribution S-9

10 from the surface current, bulk current, electrodes, and pore resistance. Since the noise RMS itself is not additive, its square is used as the vertical axis of the figures in a logarithmic scale in order to better visualize the relative amplitude of the various noise sources. Obviously, the flicker noise from the surface predominates in the low KCl concentration region, while the flicker noise from the bulk current first increases and then decreases with increasing KCl concentration. As to the noise from the electrodes and the thermal noise, they remain small in comparison with the flicker noise components. The former only effects at high KCl concentrations where the solution resistivity is low. However, the absolute noise intensity increases with increasing current bias, but the ratio of surface to bulk contribution in flicker noise does not change much. According to the model, larger current renders a higher noise level. S-10

Simulation of noise RMS and its dependence on KCl concentration and current bias for much smaller nanopores of 2 and 5 nm in diameter drilled in membranes of 1 and 2 nm thickness.

11 Simulation of noise RMS and its dependence on KCl concentration and current bias for much smaller nanopores of 2 and 5 nm in diameter drilled in membranes of 1 and 2 nm thickness. Supporting Figure S10. Variation of the noise RMS with KCl concentration and current bias for nanopores: (a) thickness H=1 nm, diameter D=2 nm, (b) H=1 nm, D=5 nm, and (c) H=2 nm, D=2 nm. In the calculations, the Hooge parameter α H is fixed at 1.9x10-4 while β is set to 1.2 and a e is taken as proportional to KCl concentration. S-11

12 Supporting Table S1. Parameters used in the model fitting in Figure 5. Parameter (unit) Value Reference N A (mol -1 ) 6.02x10 23 k (JK -1 ) 1.38x10-23 T (K) 300 μ K+ (m 2 V -1 s -1 ) 6.95x μ Cl- (m 2 V -1 s -1 ) 7.23x e (C) 1.6x10-19 σ (Cm -2 ) D, H, c In accordance to experiment S-12

13 Supporting Reference: [1] Zhang, D.; Must, I.; Netzer, N. L.; Xu, X.; Solomon, P.; Zhang, S.-L.; Zhang, Z. Direct Assessment of Solid Liquid Interface Noise in Ion Sensing Using a Differential Method. App. Phys. Lett. 2016, 108, [2] Wanunu, M.; Dadosh, T.; Ray, V.; Jin. J.; McReynolds, L.; Drndić, M. Rapid Electronic Detection of Probe-Specific MicroRNAs Using Thin NanoporeSensors. Nat. Nanotechnol. 2010, 5, 807. [3] He, Y.; Tsutsui, M.; Fan, C.; Taniguchi, M.; Kawai, T. Controlling DNA Translocation through Gate Modulation of Nanopore Wall Surface Charges. ACS Nano 2011, 5, [4] Grattarola, M.; Massobrio, G.; Martinoia, S. Modeling H + -Sensitive FET s with SPICE. IEEE Trans. Electron Devices 1992, 39, S-13

Measurement of DNA translocation dynamics in a solid-state. nanopore at 100-ns temporal resolution

Supporting Information Measurement of DNA translocation dynamics in a solid-state nanopore at 100-ns temporal resolution Siddharth Shekar 1, David Niedzwiecki 2, Chen-Chi Chien 2, Peijie Ong 3, Daniel