|Title:||Coincidence measurements of ion-induced electron emission from graphene||Other Titles:||Koinzidenzmessungen zur Ionen-induzierten Elektronenemission aus Graphene||Language:||English||Authors:||Schwestka, Janine||Qualification level:||Diploma||Advisor:||Aumayr, Friedrich||Issue Date:||2016||Number of Pages:||80||Qualification level:||Diploma||Abstract:||
With its unique properties, single layer graphene (SLG) has been considered as an outstanding candidate for many possible future applications in nano-electronics as well as in ultrafiltration. This has triggered considerable interest in the investigation of its electronic structure, and possibilities to modify this structure, e.g. by ion impact, have been investigated. In this connection collision studies with ions and the result- ing electron emission can help to improve the understanding of interaction processes between charged projectiles and this ultimately thin 2D material. In this thesis ion-induced electron emission from freestanding SLG is investigated. A new experimental setup for detecting emitted electrons in coincidence with ions traversing through the graphene has been built. Thin carbon foils, single layer graphene and its Quantifoil support have been bombarded with slow multiply charged Arq+ ions (2 -q- 9) with impact energies - 54 keV to determine the number statistics of emit- ted electrons. An evaluation routine is implemented enabling a routine calculation of the total emission yield. For obtaining the emission statistics non-negligible electron backscattering from the detector surface and various background contributions are taken into account. To gain access to contributions by kinetic and potential electron emission, measurements with varying projectile velocities and charge states are performed. A linear dependence of the electron emission yield on the ion impact velocity is found for graphene and amorphous carbon. The obtained data are compared with emission yields from highly ordered pyrolytic graphite (HOPG). The dependence on the ion charge state is observed by bombarding the examined targets with argon ions at a fixed impact energy. As expected a strong dependence on the projectile charge state is shown for all these carbon-based materials pointing to a dominant potential emission process. For bombardment with multiply charged ions SLG is found to have a higher electron emission yield compared to amorphous carbon. Within the scope of this thesis the Quantifoil support, on which the graphene is mounted, was found to be not sufficiently thick to stop Ar projectiles at these impact energies. Coincidence measurements of ion-induced electron emission are therefore not able to separate electrons originating from SLG and those from SLG on Quantifoil support. A possible solution for this problem is suggested in the Outlook of this work.
|Keywords:||Hochgeladene Ionen; Graphen; Elektronenemission
highly chared ions; graphene; electron emission
|Library ID:||AC13073757||Organisation:||E134 - Institut für Angewandte Physik||Publication Type:||Thesis
|Appears in Collections:||Thesis|
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