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Electrons Interaction with Graphene Sheets at 20 keV: Experimental Overview

Explore the interaction of electrons with graphene sheets at medium-low energies, including a new setup for 20 keV experiments and preliminary findings. Findings include transparency, impurity condensation, and current stability. Perspectives cover sample cleaning techniques and future simulation methods.

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Electrons Interaction with Graphene Sheets at 20 keV: Experimental Overview

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  1. PTOLEMY Project Electron-graphene interaction at 20 keV, overview of results and new experimental tests Ilaria RAGO,1 Maria Grazia BETTI,1Carlo MARIANI,1,* and Vittorio MORANDI2 1Dipartimento di Fisica, INFN, Università di Roma “La Sapienza” 2 CNR – IMM, Bologna *carlo.mariani@uniroma1.it (collaboration Università di Roma “La Sapienza”, CNR-IMM, Bologna) PTOLEMY Project, Laboratori Nazionali del Gran Sasso, Italy, November 26th-28th 2018

  2. outline - Graphene as potential detector - Overview of graphene-e interaction at medium-low energy - New experimental set-up for 20 keV - First data, perspectives

  3. outline - Graphene as potential detector - Overview of graphene-e interaction at medium-low energy - New experimental set-up for 20 keV - First data, perspectives

  4. graphene

  5. graphene interaction with electrons # 1-layer or few-layer graphene as sheet for transmission of electrons; # the problem of electron-graphene interaction in a wide energy range (10-20 keV); # transmission, reflection

  6. outline - Graphene as potential detector - Overview of graphene-e interaction at medium-low energy - New experimental set-up for 20 keV - First data, perspectives

  7. graphene Diffraction of a single graphene sheet grown on Ni(111) electron reflection at very low electron energies (~20 eV) Massimi et alii, Beilstein J. Nanotechnol. 5, 308 (2014)

  8. transparency of graphene at extremely low e- energies: <3 eV for electrons at these very low energies, the only expected scattering mechanism is electron-phonon (lattice) interaction graphene is deposited on a (FIB-produced) void channel in an oxide-semiconductor interface mm-thin W probe and injection of electrons through the SiO2/Si device >99% of transparency Srisonphan et alii, Sci. Reports 4, 3764 (2014)

  9. transparency of graphene at very low e- energies: 5-30 eV Au support and amorphous-C foil CVD prepared graphene/poly Cu, then transferred onto a-C/Au grid Graphene in holes of amorphous-C foil(5 keV SEM image) Hassink et alii, APL Materials 3, 076106 (2015) theoretical simulation Transparency of the order of ~80%, and <10 eV space charge effects Yan et alii, Phys. Rev. B 84, 224117 (2011)

  10. CVD prepared graphene/poly Cu, then transferred onto SiN membrane, then FIB-milled resulting in 500-1000 nm diameter holes transparency of graphene at low e- energies: 66-200 eV transparency of 73-74%-per-layer Mutus et alii, New J. Phys. 13, 063011 (2011) Longchamp et alii, Appl. Phys. Lett. 101, 113117 (2012)

  11. transparency of graphene at low e- energies: 300-1200 eV eV CVD prepared graphene on Cu or on Au Thickness-dependent transmission, exp.tal data compared with inelastic mean free path exponential attenuation model measurement of attenuated core-level XPS signal from the substrate (Cu 3p or Au 4f) Kraus et alii, Nanoscale 6, 14394 (2014)

  12. transparency of graphene at low e- energies: 300-3000 eV eV experimental transparency of: 87% 1 layer 74% 2 layers 66% 3 layers CVD prepared graphene on metal, then transferred on grid limits of the Monte Carlo simulations developed for bulk applied to mono-layers Li et alii, Adv. Functional Mat. 24, 1218 (2014)

  13. outline - Graphene as potential detector - Overview of graphene-e interaction at medium-low energy - New experimental set-up for 20 keV - First data, perspectives

  14. microscopy technique • Scanning Electron Microscope ZEISS Leo 1530 • operating between 0.1 and 30kV • InLens and Everhart & Thornley secondary electron detector • KE Developments CENTAURUS detector backscattering electron detector • aSTEM detector transmitted electrons detector • Oxford 30 mm2 SDD EDS X-Rays EDS spectrometer • Kleindik MM3A Nanomanipulators for manipulation and in-situ low noise electrical measurements

  15. Scanning Electron Microscopy (SEM) at sub-mm scale CNR-IMM @ Bologna sample holder • 5-20 keV energy • few nm diameter e- -beam • Faraday-cup, ~100 pA current scale

  16. outline - Graphene as potential detector - Overview of graphene-e interaction at medium-low energy - New experimental set-up for 20 keV - First data, perspectives

  17. graphene sheet(s) on microscopy grid

  18. graphene sheet(s) transmission current first preliminary current tests @ 5 keV electron energy I_transmitted/I_incident ~85-90% • still: • some contamination with exposure • some current instability with time •  need set-up refinement

  19. Conclusions and perspectives • * Graphene CVD-preparation and transfer to grid, cleaning by annealing * some e- -beam-induced impurity condensation on graphene * preliminary current measurements 5 keV, transparency of the order of 85-90%

  20. Conclusions and perspectives • * Graphene CVD-preparation and transfer to grid, cleaning by annealing * some e- -beam-induced impurity condensation on graphene * preliminary current measurements 5 keV, transparency of the order of 85-90% * Improvement of graphene sample cleaning (long vacuum annealing) * better current stability * n-layer statistics * new simulation methods for nm-thick layers needed

  21. Acknowledgements Ilaria RAGO (Post Doc, see talk today) and Maria Grazia BETTI fruitful discussions with Gianluca CAVOTO, Francesco PANDOLFI (see talk today), Antonello POLOSA Meganne CHRISTIAN (Post Doc), Franco CORTICELLI (techn.), Andrea MIGLIORI and Vittorio MORANDI

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