How can the electrical conductivity of graphene be measured?

[Droctagonopus]

I've tried searching for it but while there are a lot of hits on the fact that graphene's conductivity is high, there seem to be very few on how the conductivity is actually measured.

Would you use the same method as you do with metal wires? Using cross sectional area, length, an ohmmeter and calculating the resistivity from that? Graphene doesn't have a cross sectional area, does it?

How would one go about measuring its conductivity?

 

[Simon Bridge]

I've tried searching for it but while there are a lot of hits on the fact that graphene's conductivity is high, there seem to be very few on how the conductivity is actually measured.

Would you use the same method as you do with metal wires?

Pretty much ... you have to adjust the exact details to the sample but the concept is much the same.

Using cross sectional area, length, an ohmmeter and calculating the resistivity from that? Graphene doesn't have a cross sectional area, does it?

Of course it does - atoms have a thickness too. You'll find resistivity data for different directions through a sample.

How would one go about measuring its conductivity?

Off the top of my head, I'd want to sandwich a sample between two layers of something else with a small hole for the electrical contact. So I'd be measuring the conductivity of three resistors in parallel, two of which I know.

I could also just use many layers of the stuff.

See:
http://www.nobelprize.org/nobel_prizes/physics/laureates/2010/advanced-physicsprize2010.pdf

 

[Droctagonopus]

Thank you. :D

Another, kinda unrelated, question I want to ask. Would exposure to cosmic radiation, which is mainly fast moving protons affect the conductivity of a sample of graphene in any way?

 

[Simon Bridge]

The technically correct answer is "no".
This is because "conductivity" is a material property.

But I suspect you are thinking something like, "if I bias a sample of graphene and put a galvinometer in the circuit - and a cosmic ray passes through the sample, would the galvinometer needle jump?"

i.e. could you use a sheet of graphene as a particle detector?

Short answer: probably.

Note: a proton stopped in the sheet will attract an electron - which slightly changes the current.
This is a really small effect, and considering how thin graphene sheets gets to be, an unlikely one.
To exploit graphene for particle detection you have to get clever.

Fox M. (2012) http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6144014&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6144014 IEEE Transactions in Nanotechnology May 2012

It's an area of active development.