Figure 1

(Color online) (a) Scanning electron microscope image of the constriction in sample Nano1 before electromigration. (b) Typical SEM image of a nanogap after electromigration and measurements at low temperature. (c) Current-voltage characteristics during the electromigration process. Right inset: conductance plateaus observed during the last ramp. Left inset: schematic representation of the electromigration and measurements setup. The $R_S=150\Omega$ series resistance is due to the wiring.Reuse & Permissions

Figure 2

(Color online) (a) and (b): current-voltage characteristic of sample Nano1 and Nano5 (open blue dots). (c): Data of sample Nano1 in the Fowler-Nordheim representation. The shape of the tunnel barrier used to model transport is represented in three different region (i) $-{\phi }_L<V<0$, (ii) $V<-{\phi }_L$, (iii) $0<V<{\phi }_R$. Solid lines: fits to the 1D model (black) and to the planar junction model (red) with $A=10{\text{nm}}^2$. Curves are not distinguishable. The used fit parameters for the 1D (planar) model are ${\phi }_L=0.29\text{eV}\left(0.23\text{eV}\right)$, ${\phi }_R=0.95\text{eV}\left(1\text{eV}\right)$, and $d=1.18\text{nm}\left(1.31\text{nm}\right)$ for sample Nano1 and ${\phi }_L=1.24\text{eV}\left(1.25\text{eV}\right)$, ${\phi }_R=0.35\text{eV}\left(0.31\text{eV}\right)$, and $d=1.79\text{nm}\left(1.88\text{nm}\right)$ for sample Nano5.Reuse & Permissions

Figure 3

(Color online) (a) Current-voltage characteristic of sample Nano1 (open blue dots) on a logarithmic scale compared to the fits based on the 1D model (black dashed line) and the planar junction model (red line). (b) Expanded view of the data (open dots and squares) of sample Nano1 near the minimum of the Fowler-Nordheim representation. Black dashed line: fit to the 1D model using the following parameters ${\phi }_L=0.29\text{eV}$, ${\phi }_R=0.95\text{eV}$, and $d=1.18\text{nm}$. Solid colored lines: fit to the planar junction model when varying the area $A$ of the nanogap cross section (from top to bottom at the minimum, green $A=1{\text{nm}}^2$, red $A=10{\text{nm}}^2$, and purple $A=100{\text{nm}}^2$). The best fit is obtained for $A=10{\text{nm}}^2$, ${\phi }_L=0.23\text{eV}$, ${\phi }_R=1.00\text{eV}$, and $d=1.31\text{nm}$.Reuse & Permissions