Surface scattering dynamics of graphene and graphite

by Sven Meyer
Doctoral thesis
Date of Examination:2022-03-15
Date of issue:2022-04-26
Advisor:Prof. Dr. Alec M. Wodtke
Referee:Prof. Dr. Alec M. Wodtke
Referee:Prof. Dr. Martin A. Suhm
Referee:Prof. Dr. Jürgen Troe
Referee:Prof. Dr. Theofanis N. Kitsopoulos
Referee:Prof. Dr. Dirk Schwarzer
Referee:Dr. Daniel Steil
Persistent Address: http://dx.doi.org/10.53846/goediss-9197

 

 

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Abstract

English

Since its first successful preparation in 2004, graphene has been extensively studied because of its outstanding mechanical, thermal and electronic properties. Graphene is an especially interesting material because of its zero-bandgap electronic structure, which puts it right on the edge between metals and semiconductors. Up to this point, non-adiabatic interactions have only been observed on metal surfaces. In this work, vibrational excitation of NO was investigated as a probe for non-adiabatic interactions by scattering a molecular beam of NO from epitaxial graphene on Pt(111) (Gr/Pt) and highly oriented pyrolytic graphite (HOPG). No signs of non-adiabatic interactions were found. Instead, thermal vibrational excitation of NO was observed on Gr/Pt as a result of a trapping-desorption scattering mechanism, which is supported by state to state time of flight measurements. In contrast, on HOPG only direct scattering without vibrational excitation has been observed. Further state to state time of flight experiments revealed a very efficient coupling between the surface and the kinetic energy of the NO, resulting in a high translational energy loss of up to 80% for Gr/Pt, and up to 66% for HOPG. An enhanced sticking probability of NO on graphene compared to HOPG was observed that could be modeled using detailed balance. This enhanced sticking probability makes graphene an interesting substrate for catalysts, where it can act as a net to catch the reactands.
Keywords: Dynamics at surfaces; Molecular beam surface scattering; REMPI spectroscopy; Energy transfer; Detailed balance; Vibrationally excited NO; vibrational relaxation; Graphene
 
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