Fig. 3: Electron transport in 9-AGNR transistors (D3 and D6) with M-SWNT leads.
From: Contacting individual graphene nanoribbons using carbon nanotube electrodes
a,b, Single-electron charging behaviour in D3. Colour-scaled differential conductance versus VFG and VBias at fixed VSG1 = VSG2 = 4 V, showing single-electron charging behaviour (a). Close-up of the box in a (white dotted line), highlighting the excited states (green arrows) and lead states (blue arrow) (b). c–e, Franck–Condon blockade in D6. Colour-scaled differential conductance versus VFG and VBias for VSG1 = VSG2 = 0 V (c). Low-bias conductance is suppressed and the Coulomb blockade cannot be lifted by VFG. Periodic excitations (white arrows) appear within the conductive regime at positive and negative biases. NDC appears in some regions (green colour). d, Schematic of the Franck–Condon model for strong electron–phonon coupling λ, with N (blue curve) and N + 1 (green curve) electrons in the QD. The tunnelling electron shifts the equilibrium coordinate of the phonon harmonic oscillator by an amount proportional to λ, thereby exponentially suppressing the transition between the vibrational ground states of the N and N + 1 charge states. e, Differential conductance measured for VFG = 2.48 V and VSG1 = VSG2 = 0 V. The representative fit of the maxima with the Franck–Condon progression (equation (1)) enables us to extract the coupling as λ = 2.65.
