Discussion Forum

There are published papers about graphene. A quick web search finds, among others: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6474003/ Just type "electrical conductivity of graphene" into a search engine. Once you identify the value (or values) for its electrical conducticity in your circumstances, plus any other important/needed physical properties of graphene in your model, then you can then define your own material as (for example) "MyGraphene," just as you would any other user-defined material in Comsol Multiphysics.

The conductivity is depending on direction, in one direction its metallic, and in the other its semiconducting (x and y along the surface directions). In the conducting direction, lets say x we have as the attached figure says. Number of quantum conductance 2e^2/hN, where N=aD, and a=0.01nm, and D=diameter of graphene flake/ribbon. Tried simple model with isotropic resistivity (not as I mention above) to use the Contact Impedance, using surface impedance with: surface resistance=Ac/sigG, where sigG=Nc2e_const^2/h_const and Nc=2a/0.01[nm]. It should be better than silver, but it seems comsol only sort of add this resistivity to the bulk resistivity, and nothing interesting happens. rhoBulk=1 and Ac=pia^2, a=0.1 in the model.

To see a more realistic effect i used floating potential on the circle flake instead. The potatial of a metallic flake should be constant over the flake. This works fine. Havn't foond a way to "fool" comsol to do it in the right way. I guess it has to be done with weak formulation...