A Bottom-Electrode Contact: The Most Suitable Structure for Graphene Electronics

The high contact resistivity of graphene, which is caused by its low density of states (DOS) at the Dirac point, is a major restriction for realizing low-voltage, high-speed graphene electronics. The bottom-electrode contact is known to have a lower contact resistivity than the top-electrode contact for graphene devices. However, it is not studied extensively enough to confirm its validity. Here, the contact resistivity of graphene on Pt as a bottom-electrode in single-layer graphene field-effect transistors is investigated and its extremely low contact resistivity whose value is cross-checked with various methods is successfully demonstrated. The absence of a significant difference in resistance measured by two-probe and four-probe methods indicates that the contact resistivity is insignificant. This extremely low resistivity (as low as 2.82 omega mu m), achieved without additional processes, such as doping or creation of artificial edges, is attributed to enhanced DOS in graphene edges with the bottom-electrode contact. Unlike other reports, the contact resistivity remains constant with the increase in width of graphene-metal contact, and it is lowest at the Dirac point, and this is the evidence of the current flowing along graphene edges. All observations strongly suggest that the bottom-electrode contact is the most suitable structure for graphene electronics.

Automated summary

This study investigates the impact of bottom-electrode contact on graphene devices and demonstrates the ability to achieve extremely low contact resistivity. The enhanced density of states (DOS) at the bottom-electrode contact is the key factor for achieving low resistivity.