Positron induced electron emission from graphene

We report here the energy spectra of positron-induced electrons emitted from single- and multilayer graphene films. One of UT Arlington’s two Time of Flight positron beam systems was used to deposit very low energy (KE < 1.5 eV) positrons at the surface of graphene samples consisting of a) 1 layer of graphene on polycrystalline Cu and b) 6-8 layers of graphene deposited on polycrystalline Cu. A time of flight spectrometer was used to measure the energy of positron-induced electrons. A peak in the electron energy spectrum was observed at ~263 eV corresponding to annihilation induced Auger electrons as a result of the KVV transition from the two graphene samples, which were comparable in intensity to that observed from a bulk graphite sample. In addition, we have observed a low energy peak in the annihilation induced electron energy spectra from graphene which extends up to ~15 eV. Our observation that the positron annihilation induced KVV Auger signal from graphene has a significant intensity indicates that the low energy positrons can be efficiently trapped on the surface of graphene layer on Cu down to a single-layer.