We had made a layer of few nm thick layer of graphene and want to get its electrical characteristics,please tell any method to get the electrical contact on this thin layer|?
You can try to apply Carbon (or Ag) paste (for a glass substrate) electrical contacts[1], on top of the graphene layer. As (an electrode contacts') topology, you can try to apply both :
1) the Van der Pauw, 4-point method, and if it fails[2],, you can try to extend the point contacts to the next contacts' dimension, e.g. to
2) a 4-lines contacts and you can apply a (near) classical method
to measure the conductivity of the graphene film.
1. As well as you can try to deposit a Pt, etc. electrical contacts' layer.
2. It might fail, if there are pinholes etc. in the graphene layer.
We can apply a few blind (as a bat) point contacts[1,2], even some more than 4 (needful for the Van der Pauw); and we can use a topological electrifying combo of these point contacts for the electrical measurements of the eyeless (monolayer) graphene on the glass substrate.
1. Engineers Make Electrical Contact to Graphene on It's 1-Atom-Thick Edge https://spectrum.ieee.org/nanoclast/semiconductors/nanotechnology/engineers-make-electrical-contact-to-graphene-on-its-1-atom-thick-edge
2. Electrical Contacts in Monolayer Arsenene Devices http://pubs.acs.org/doi/abs/10.1021/acsami.7b08513
I would do electron beam lithography (with PMMA) and metal deposition, for instance, Ti/Au (2/30nm or so). This what the people do. Other methods mentioned above are not possible (perhaps with CVD...but still are super bad suggestions)