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Flowchart of the graphene nanoribbon device fabrication. (a) Mechanical exfoliation of graphene onto a Si/SiO2 substrate with markers, followed by deposition of CdSe nanowires. (b) The wires serve as etching mask during subsequent reactive ion etching. (c) After wet etching of the wires, the ribbons are provided with metal contacts. (d) AFM image of a 22 nm wide GNR device. The distance in between the contacts is 1.5 μm.
Electrical characterization of GNR devices under ambient conditions. (a) Electrical resistance as a function of VGS for the device shown in Fig. 1(d) (VDirac = +10 V in this case). Inset: ID vs. VDS curve at the Dirac point. (b) On/off ratio plotted against ribbon width. The on conductance is measured in the p-type regime at VGS -VDirac = −30 V. In total 24 GNR devices on three different chips (assigned by black squares, red circles, and blue triangles, respectively) were evaluated.
SPCM measurements of the device in Fig. 1(d) (step size ∼62 nm). (a) Optical reflection image recorded during the photocurrent measurement, revealing the two metal contacts. (b) SPCM image in the p-type regime of the device (VGS -VDirac = −36 V, VDS = 0 V). The two photocurrent peaks are, respectively, denoted as S and D, according to their nearby electrodes. (c) SPCM image recorded in the n-type regime at VGS -VDirac = +20 V.
(a) Photocurrent detected close to the metal contact in dependence of the GNR width. The gate voltage was adjusted to VGS ∼ −30 V for the p-type regime, and VGS ∼ +30 V in the case of n-type regime. Error bars correspond to the standard deviation by averaging over several measurements. (b) Photocurrent (black squares) and calculated photovoltage values (red circles) in dependence of the inverse of the measured ohmic resistance of several GNR devices. (c) Equivalent circuit model to account for the results in panel (b).
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