Making consistent contacts to graphene: effect of architecture and growth induced defects

Abstract

The effect of contact architecture, graphene defect density and metal-semiconductor work function difference on resistivity of metal-graphene contacts have been investigated. An architecture with metal on the bottom of graphene is found to yield resistivities that are lower, by a factor of 4, and most consistent as compared to metal on top of graphene. Growth defects in graphene film were found to further reduce resistivity by a factor of 2. Using a combination of method and metal used, the contact resistivity of graphene has been decreased by a factor of 10 to 1200 ± 250 Ωµm using Palladium as the contact metal. While the improved consistency is due to the metal being able to contact uncontaminanted graphene in the metal on the bottom architecture, lower contact resistivities observed on defective graphene with the same metal is attributed to the increased number of modes of quantum transport in the channel.

The role of contact resistance in graphene field-effect devices

“…9). reported that also growth defects may reduce the contact resistivity by a factor of two [118]. Indeed, the contact resistivity for Pt, Au and Pd, obtained at carrier concentration varying from −1.5 to +1.5 × 10 12 cm −2 , have been measured for two different defect densities, showing that for each metal, the graphene with higher defect density has a lower resistivity.…”

“…A way to improve the contact resistance is using a suitable device architecture. With respect the standard configuration, in which the metal is deposited on top of graphene layer, it has been shown that by realizing a "metal-on-bottom" configuration [118], the contact resistance may be improved.…”

Effects of Different Ion Irradiation on the Contact Resistance of Pd/Graphene Contacts

“…However, although contact resistance is an important obstacle for further improvement, which is still not well understood. Conventional deposition of metal electrodes on top of the graphene surface often resulted in a large contact resistance [5,6,7]. In order to modify the Fermi level difference between metal and graphene to improve the metal/graphene (M/G) interface, distinct metals with different work functions were initially attempted [8].…”

Growth Mechanism for Low Temperature PVD Graphene Synthesis on Copper Using Amorphous Carbon

“…A worth-noting point observed in our samples is that the I D peak intensity, which is also connected with defects, is on a higher side but these defects are advantageous with respect to contact resistance on metals4243, and thus will be beneficial for ULSI Interconnects’ applications.…”