Fig. 4

Multi-channel single-electron tunnelling transistors based on the GQDs of 13 nm in size. a The low excitation measurements of low bias region of b. Thin and long green arrows indicate the tunnelling events through the localised states in the middle hBN layer. Thick and short arrows indicate the edges of the Coulomb diamonds (red), and the resonances from localised impurity states (green) crossing the white dashed line (G(V_g = −24V, V_b), presented on d). b Conductance G(V_g,V_b) measured at T = 250 mK. The red (blue) dashed line mark the event of the Fermi level in the top (bottom) graphene layer aligning with the Dirac point. Red arrows indicate the edges of the Coulomb diamonds crossing the white dashed line (G(V_g, V_b = 63 mV), presented on e). c The magnified plot of b denoting the peculiar shape of Coulomb diamonds when the Fermi level in one of the graphene contacts aligns with the Dirac point (black arrow). The dashed white line indicates the cross-section presented in f. d The plot of conductance G(V_g = −24V,V_b) from a. Thick and short arrows indicate the same events as in a: the edges of the Coulomb diamonds (red), and the resonances from localised impurity states (green). e The conductance G(V_g, V_b = 63 mV) plot. Red arrows indicate the same events as in b: edges of the Coulomb diamonds. The inset shows the schematic structure of the van der Waals stack. Graphene contacts are separated by hexagonal boron nitride layers from the GQD-hBN layer. Carbon atoms are blue, boron—yellow, nitrogen—purple. f The conductance G(V_g, V_b = 0 mV) plot from c (marked by white dashed line)