  Vertical graphene heterostructures have been introduced as an alternative
architecture for electronic devices by using quantum tunneling. Here, we
present that the current on/off ratio of vertical graphene field-effect
transistors is enhanced by using an armchair graphene nanoribbon as an
electrode. Moreover, we report spin-dependent tunneling current of the
graphene/MoS2 heterostructures. When an atomically thin MoS2 layer sandwiched
between graphene electrodes becomes magnetic, Dirac fermions with different
spins feel different height of the tunnel barrier, leading to spin-dependent
tunneling. Our finding will develop the present graphene heterostructures for
electronic devices by improving the device performance and by adding the
possibility of spintronics based on graphene.
