When calculate the conductivity of graphene(σ=neμ), I find that the unit of carrier density is cm^-2. So the unit of σ is S (Siemen). But in simconductor, the unit of carrier density is cm^-2, leading the unit of σ to S/m. This puzzles me a lot!! Thanks!
Thank you very much!
I know this derivation process！
The question is that this result is quite different from that in simconductor.In simconductor,the unit of n is cm^-3.so the unit of ne is C/cm^3.This can lead the uint of σ in simconduct to be S/m, which is different from your result!! And this is the common unit of σ in both simconduct and metal!
Thank you again for you consideration!
Dear Sirs,
the difference in the unit of the conductance just results from the 2-dimensional nature of graphene.
For 3-dimensional bulk materials, the unit of conductance is [1/(Ohm x Meter)], as derived from a charge carrier density of [Coulomb/Meter^3]. The latter definition, i.e. charge per volume, makes no sense for a 2-dimensional sheet of material, such as graphene.
Calculating the conductance for a 2-dimensional sheet with with a charge carrier density in terms of charge per area, i.e. [Coulomb/meter^2], then results in [1/Ohm] as the unit of conductance. In the 2-dimensional case, the units of conductance and conductivity are the same. Don´t confuse!
Sincerely, FM
It should be the same as in the 3D case, but instead of taking the cross section area only the width of the flake is used. Then, the dimensions of length/width cancel each other and everything is alright!
In case that the flake is of irregular shape, just approximate is by an array of regular shaped flakes and consider it as circuit of parallel resistors and/or resistors in series.
Regards, FM
Dear Frank Müller and Fuwei Qiu ,
Okay than what is the conductivity of X sample in CGS unit?
The x sample (30 micron thick) has 58.1*10^6 1/(Ohm*meter) conductivity in SI unit.
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