Figure 1

(a) Schematic illustration of a percolating-tunneling system showing a gap in the critical path (solid line), and additional tunneling paths (dashed lines). (b) SEM micrograph and (c) onset of conductance as a function of deposition time for a typical sample. The steps in conductance coincide with integral multiples of $G_0$. (d) Histogram of conductance values measured during the onset of conductance in 21 samples, showing clear peaks at integral multiples of $G_0$. (e) Schematic depiction of EFIE and (f) EFISD or van der Waals forces.Reuse & Permissions

Figure 2

(a) Conductance of a $10\times 20\mu \mathrm{m}$ sample (solid line) showing downward steps under an applied voltage (dashed line). (b) Histogram of conductance data from all 67 samples showing a clear peak at $G_0$, and much weaker peaks near $2G_0$ and 3 $G_0$. All data were collected while ramping the applied voltage.Reuse & Permissions

Figure 3

(a) Typical multilevel switching behavior under an applied voltage ramp. (b) Example of repeatable switching between the same two conductance levels. (c) Conductance data for a sample in the tunneling regime. (d) $I(V)$ behavior for the same sample as in (c). The exponential increase is clear evidence for tunnel gaps. The data for $V\le 2V$ are noise and should be ignored.Reuse & Permissions

Figure 4

Results of continuum percolation model, for system size $200\times 200$ particles and $A=1$ and $\beta =100$ (corresponding to a tunneling length scale of 0.01 particle diameters). (a) Histogram of system conductance values prior to [dark gray (blue)] and after [light gray (red)] insertion of a quantum conductance ($G=G_0$) in the gap with the highest electric field, for $p=0.675$. (b) Probability of observation of quantized conductance for the system as a function of $p$.Reuse & Permissions