Figure 1

(a) Schematic illustration of an etched nanoribbon with width $W$, highlighting local charge islands along the ribbon. (b) Scanning force microscope image of an etched graphene nanoribbon (GNR) with a nearby single-electron transistor (SET) and lateral gates (PG, SG1 and SG2). (c) Low bias ($V_b=300\mu \mathrm{V}$) back-gate characteristics of the GNR showing that the regimes of hole and electron transport are separated by the transport gap, indicated by the vertical arrows. (d) High resolution close-up inside the gap displaying a large number of sharp resonances within the gap region. (e) Close-up of a single resonance [see arrow in panel (d)].Reuse & Permissions

Figure 2

(a) Current measurements as function of bias and back-gate voltage (all other gates are grounded) on the 45 nm wide nanoribbon [Fig. 1a]. The white areas are regions of strongly suppressed current forming the energy gap. The inset shows a typical nonlinear $I\mathrm{\text{−}}V$ characteristic ($V_{\mathrm{bg}}=10.63\mathrm{V}$, see arrow). (b,c) Differential conductance ($G$) measurements as close-ups of panel (a) at two different back-gate regimes [see labels in (a)]. These measurements show diamonds with suppressed conductance (highlighted by dashed lines) allowing to extract the charging energy from individual diamonds. (d) Charging energies as function of the back-gate voltage over a wide range.Reuse & Permissions

Figure 3

(a) Low bias ($V_b=300\mu \mathrm{V}$) conductance measurements as function of plunger gate voltage at fixed back gate ($V_{\mathrm{bg}}=7\mathrm{V}$), showing a large number of sharp resonances within the gap region. (b) Corresponding diamonds [see highlighted area in panel (a)] in differential conductance $G$ [same color scale as in Figs. 2b, 2c]. Here, a dc bias $V_b$ with a small ac modulation ($50\mu \mathrm{V}$) is applied symmetrically across the ribbon. (c,d) Charge stability diagrams as function of plunger gate and back-gate voltage (c) and side gate 1 and back-gate voltage (d). These plots highlight that individual resonances have individual lever arms (see dashed and dotted lines). (e,f) Detection of individual charging events in the nanoribbon by the nearby SET. (e) Coulomb blockade resonances on the SET as function of $V_{\mathrm{pg}}$ and $V_{\mathrm{bg}}$ exhibit clear signatures of the charging event in the nanoribbon expressed by crossing the local resonance (f). Dotted and dashed lines show the different lever arms.Reuse & Permissions

Figure 4

Illustration of the potential landscape along the graphene nanoribbon allowing the formation of charged islands and quantum dots. For more details see text.Reuse & Permissions