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(Color online) (a) TEM image of a device showing the front gate (length Lg = 29 nm), channel (thickness TSi = 12 nm), and BOX. The gate oxide thickness is 5 nm. (b) TEM image on a larger scale showing the various voltages applied during measurement; in particular, the back gate substrate voltage (Vbg ) applied across the BOX (150 nm thick).
(Color online) (a) Sample 1: Drain-source conductance G versus front gate voltage Vg at 300 K for various Vbg , ranging from 0 (bottom) to 39 V (top). (b) Evolution of the threshold voltage Vt with Vbg . The sub-threshold swing of 70 mV/decade is nearly independent of Vbg . (c) Drain-source conductance at Vg = Vt + 1.6 V, i.e., corrected for the shift of Vt . Note that it increases significantly with Vbg .
(Color online) (a) Sample 1: G versus Vg (Vd = 100 μV) at 1 K for Vbg = 0, 12, 15, 18, 39 V (from top to bottom). The curves have been shifted horizontally to show the onset of current (Voffset = 400, −30, −210, −300, −890 mV, respectively). At Vbg = 0 V and 12 V, regular CBOs are observed. At Vbg = 39 V, only very few aperiodic and broad features are observed attributed to residual single impurity effects. The crossover does not depend on the absolute value of the conductance G but on Vbg only. (b) Schematic picture of the device in the SET regime (top) and in the FET regime (bottom). The dotted areas correspond to high doping region acting as source drain reservoirs at low temperature. An electron gas (green shaded area) is either induced by the front gate (SET regime) or by the back gate (FET regime).
(Color online) (a) Sample 2: Coulomb blockade oscillations in the source-drain conductance G versus gate voltage at zero back gate voltage. (b) The characteristic of the same device at Vbg = +20 V (red curve). The Coulomb oscillations are replaced by a typical field-effect curve showing an excellent sub-threshold slope of 8 mV/decade. For comparison, the characteristic at 300 K and Vbg = 0 V is also shown.
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