  Graphene is a single layer of carbon atoms arranged in a honeycomb lattice
with remarkable mechanical and electrical properties. Regarded as the thinnest
and narrowest conductive mesh, it has drastically different transmission
behaviours when bombarded with electrons and ions in vacuum. This property, if
confirmed in gas, may be a definitive solution for the ion back-flow problem in
gaseous detectors. In order to ascertain this aspect, graphene layers of
dimensions of about 2x2cm$^2$, grown on a copper substrate, are transferred
onto a flat metal surface with holes, so that the graphene layer is freely
suspended. The graphene and the support are installed into a gaseous detector
equipped with a triple Gaseous Electron Multiplier (GEM), and the transparency
properties to electrons and ions are studied in gas as a function of the
electric fields. The techniques to produce the graphene samples are described,
and we report on preliminary tests of graphene-coated GEMs.
