Figure 4. Electronic transport through GNR devices on h-BN.

(a) Conductance (G) of GNRs with a width of ∼15 nm as a function of the back gate voltage (V_gate) at different temperatures; (b) Arrhenius plot of the resistance of the 15-nm GNR FET under different V_gate values at temperatures from 2 to 250 K. The solid curves are fits based on a simple two-band (STB) model (see Supplementary Note 3); (c) Electronic transport through a narrow ribbon with a width of ∼5 nm. Its conductance can be completely switched off, even at 300 K. The inset shows the conductance at V_gate=−30 V versus inverse temperature from 200 to 300 K. The dashed line is fit to the experimental data according to ; (d) Band gap E_g extracted from experimental data for GNRs versus their ribbon width (w). The orange curve is a fit of our experimental data with E_g (eV)∼α/(w+β) (α is in units of eV nm, both β and w are in units of nm). The light purple (α=0.8 eV nm) and light green curves (α=1.0 eV nm) are empirical curves adapted from ref. 9 and refs ²⁴, ²⁵, respectively. Error bars for the experimental data represent standard deviation of uncertainty in AFM measurement or gap extraction.