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(a) Transmission-electron microscope (TEM) micrograph of a self-assembled chain of Au NCs coated with octanethiol molecules; arrows indicate parallel crystal facets. (b) Double-island device fabricated by contacting a self-assembled chain of NCs. The two NCs framing the two island particles form part of the electrodes, such that all three tunnel junctions are formed by self-assembly and not by lithography.
Experimental and predicted differential conductance plots of the double-island device of Fig. 1(b). (a) Differential conductance measured at ; four peaks are found per gate period. Above the threshold for the Coulomb blockade, the current can be described as linear with small oscillations superposed, which give the peaks in . The linear component corresponds to a resistance of . (b) Electrical modeling of the device. The silicon substrate functions as a common gate electrode for both islands. (c) Monte Carlo simulation of a stability plot for the double-island device at with capacitance values obtained from finite-element modeling: (island-gate capacitance), (interisland capacitance), (lead-island capacitance); the left, middle and right tunnel junction resistances were, respectively, set to 0.1, 10, and to reproduce the experimental data.
(Color online) Characteristics of a double-island device. (a) The number of tunneling channels accessible as a function of and . At the numbers of electrons on each island is constant inside the white diamonds. At higher tunneling channels open for either electrons or holes. The conduction channels are bounded by lines, the positions and slopes ( and ) of which only depend on the device capacitances , , . denotes the interisland capacitive coupling ratio. The tunneling states for are omitted for clarity. (b) A fit of the double-island differential conductance data shown Fig. 2(a) (background picture) with the conductivity jumps expected from the diagram in (a). The fitting parameters are listed in the inset.
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