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(Color) (a) SEM image of a typical device. The Al SET island forms during the second of two evaporations at different angles. (b) Schematic of the measurement circuit. The conductance of each SET is measured using independent circuits. The red region represents the MOSFET conducting channel confined between the two regions. The circles containing the letter “A” represent current-sensitive amplifiers. (c) Coulomb blockade oscillations of the Si SET differential conductance as a function of the relative bias between the Al SET and the Si SET at .
(Color) Simultaneously measured conductances of both SETs. [(a) and (c)] Coulomb blockade oscillations of the Al and Si SET conductances, respectively, at . [(b) and (d)] Conductance of the Al and the Si SET, respectively, vs and .
(Color) Conductance maxima of both SETs vs and . Red dots and blue dots are Gaussian fits to the data in Figs. 2(b) and 2(d), respectively. Black lines are a linear fit to the points on each edge. The regions labeled a, b, c, and d are the four hexagons whose parameters are presented in Table I.
(Color) (a) Circuit model for the coupled SET system. and are the number of electrons on the Al and the Si SET island, respectively. Due to the very small drain-source bias of each SET, we can simplify the two tunnel barrier capacitances for each SET to a single capacitance ( and ) as shown. (b) Hexagonal phase diagram based on the model in (a). Each hexagon represents a configuration with a different number of charges on the SET islands. , , and are the slopes of the hexagon edges. , , and are the separations between opposite parallel edges of the hexagon.
Capacitances of the four hexagons labeled in Fig. 3 for the circuit model in Fig. 4.
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