Danish researchers have for the first time mapped the carrier mobility and density of large sheets of graphene with electromagnetic radiation.
For the last decade, the usual way of measuring the electronic properties of graphene – in particular the carrier mobility and carrier density, which together give the sheet conductance – has been to fabricate a transistor-like device and electronically measure how the conductance changes as a function of applied electrostatic gate voltage. This all-electronic approach is best when dealing with small pieces of graphene, such as the microscopic flakes produced by micromechanical cleavage (also known as the 'scotch-tape method') – however, advances in graphene production techniques now allow us to continuously produce large areas of graphene meters across. Producing and measuring thousands or millions of microscopic devices from such sheets would be impractical and would reduce the useful area of graphene for the intended application. We need to be able to check the electronic properties of such large regions without destroying them in the process.
Read more at: http://phys.org/news/2015-07-illuminating-electronic-properties-graphene.html#jCp