Fig. 2.

Electron tunneling in few-layer CrI₃ vertical junctions. a Current measured on the device shown in Fig. 1d as a function of bias applied between the graphene contacts for T ranging from 0.25 to 70 K (the intermediate temperatures are 10, 20, 30, 40, 50, and 60 K). Below T = 20 K, the I–V curves become temperature independent as shown in the inset, indicating that transport is determined by tunneling (the overlapping area of the graphene contacts is 4 µm² and the thickness of the CrI₃ layer is ~7 nm). b Arrhenius plot of the resistance measured at different bias voltages (0.35, 0.5, and 0.7 V). c In the tunneling regime (i.e., for T < 20 K), ln(I/V²) is linearly proportional to 1/V, as expected for Fowler-Nordheim tunneling (charge carriers tunnel into the conduction band through band-gap of CrI₃ that is tilted by the applied bias forming a triangular barrier, as illustrated schematically in the inset). The different curves correspond to measurements performed at the same temperatures as in a