Intentionally created localized bridges for electron transport through graphene monolayer between two metals

Monolayer graphene (1LG) is frequently unpredictably modified by supporting material so that it limits development of devices. Van der Waals interaction is dominant in the models describing the in-plane processes, including the electrical charge transport. However, the current flow perpendicular to the plane of the graphene is still less understood. This report analysed specific aspect of the perpendicular current and disclosed an original way to create transport bridges perpendicular to the plane across the 1LG. The most extraordinary finding is that the electron transport between two parallel metal surfaces can be shut down and opened if the metals are separated by the 1LG. The electron transmission can be intentionally varied in this metal-1LG-metal (M-G-M) system by pressure. In the experimental study the AFM force curve and tunnelling current measurements were combined when the external load force (0-1200 nN) and electrical potential (-1.5 V to +1.5 V) were used. It is proved that for low voltages (<±9 mV) a bridge is opened perpendicular to the graphene across the M-G-M systems by the external force, if the compression dependent Fermi level crosses electronic states in the interfaces and graphene. The localised bridges with diameter about 10-40 nm can be opened and kept continuously by the stabilised force in separated points of the system. However, the predictable changes can be produced in the system if the voltage and the force exceeded critical magnitudes. A combined model was proposed acceptable to explain the bridging and predictably modify the characteristics.