Speaker
Description
The study of 2D materials, and in particular their interaction with low-energy electrons, is of great interest in surface physics, as well as in several applications ranging from the development of electronic devices to novel detectors for particle physics. The concept of graphene as a pressure-tight membrane transparent to electrons can be employed for the upgrade of MPGD detectors, like Micromegas and GEMs, and for the development of novel ones. We report on the in-vacuum transmission of low-energy electrons through monolayer and trilayer graphene suspended on transmission electron microscopy (TEM) grids. Polycrystalline graphene was grown on copper via chemical vapor deposition (CVD) and transferred onto the TEM grids at the CNI@NEST of Pisa. The custom-made monochromatic electron gun of the LASEC laboratory at Università Roma Tre has been employed to perform the transmission measurements. The electron beam has tuneable energy in the 30 -900 eV range with a resolution of 45 meV and a very good current stability. We measured the in-vacuum (~10-9 mbar) transmission of graphene layer(s) suspended on the grids as a function of the electron energy with currents in the 200 pA range. The experimental apparatus allows to measure with a Faraday cup either the electron gun emitted current or the current transmitted through the graphene. Thus the transmission is obtained as the ratio of these two measured values. Moreover, a thorough characterisation of the graphene samples has been performed in order to check the quality and the grids coverage with three spectroscopic techniques: micro-Raman, X-ray photoemission and electron energy loss.
