Figure 1

(a) Transmission electron microscopy image of a nanopore (diameter 9.8 nm). The scale bar is 10 nm. (b) Conductance of a 12.7 nm diameter pore, measured at 100 mV, as a function of laser position relative to the focus. A schematic representation of a nanopore moving through the laser focus at three different positions is shown in the inset.Reuse & Permissions

Figure 2

Conductance as a function of position relative to the laser focus for two nanopores with a diameter of 5.6 nm (a) and 11.1 nm (b), measured at 500 and 200 mV, respectively. The two lower curves in (a) display a decreased conductance and a dramatic increase in noise. In (b) the conductance instantaneously switches between two (red curve) or three (blue curve) different values each displaying different noise characteristics. The blue curve is scanned up to $Z=0$ only. Current histograms (c) and power spectra (d) show the strong differences in current noise of the curves shown in (b). The histograms are centered around zero by shifting each distribution by $I_0$, the peak value of a Gaussian fit. The red and blue histograms are magnified along the $Y$ axis in order to be visible on the same scale. The inset in (c) shows the total current distribution of the blue curve. The red curve is analyzed before and after switching to the decreased conductance state. Before switching the red histogram in (c) does overlap with the data shown in black. In (d) the current power spectral density before and after the switching is represented by open and filled red circles, respectively. The low-frequency noise has a $S_I\propto 1/f^{\alpha }$ frequency dependence with $\alpha =1.1–1.9$. The lines are guides to the eye.Reuse & Permissions

Figure 3

(a) Two typical scans of the conductance of a 7.2 nm diameter nanopore, measured at 50 mV, as a function of laser position relative to the focus. The bottom curve clearly shows a double-peak conductance profile in addition to a reduced conductance for all $Z$ positions. (b) Model curves (see text) of the conductance as a function of laser position relative to the focus for different values of the diameter of the nanobubble, $d_{b0}$ at temperature $T_0$. The inset shows a schematic representation of the model. A cylindrical nanopore, with a nanobubble present, moves through the focus of the laser. The nanobubble expands near the focal position as a result of higher local temperatures.Reuse & Permissions