AVS 65th International Symposium & Exhibition
    Surface Science Division Thursday Sessions
       Session SS+EM+NS-ThM

Paper SS+EM+NS-ThM5
Intercalation of O2 and CO between Graphene and Ru(0001) and the Role of Defects

Thursday, October 25, 2018, 9:20 am, Room 203C

Session: Defects in and Functionalization of 2D Materials
Presenter: Jory Yarmoff, University of California, Riverside
Authors: J.A. Yarmoff, University of California, Riverside
T. Li, University of California, Riverside
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Graphene (Gr) is a fascinating 2D material that is being widely being considered for applications in electronic devices due to its unique electronic and materials properties. Also, because of its high thermal stability and inertness, it is a promising candidate for use as a protection layer for metal substrates. Here, graphene films grown on Ru(0001) are exposed to O2 and 13CO and investigated with helium low energy ion scattering (LEIS). LEIS spectra collected at different scattering angles can distinguish between adsorbed and intercalated molecules. It is found that O2 and CO do not adsorb to the graphene surface but instead intercalate between Gr and the substrate. It is shown that a much lower annealing temperature is needed to remove intercalated oxygen than chemisorbed oxygen on bare Ru. During the thermal desorption, some of the graphene is etched away via chemical reaction forming gaseous CO or CO2. In addition, carbon vacancy defects are produced in the Gr films via 50 eV Ar+ bombardment. Isolated single carbon vacancy defects enable molecular adsorption at the defect sites and ease the overall intercalation of oxygen. The defects also improve the thermal etching efficiency of Gr by intercalated oxygen. When the defects are large enough to consist of open areas of bare substrate, oxygen dissociatively chemisorbs to Ru. Intercalated 13CO molecules sit upright with the O end on top, as on clean Ru. The CO molecules tilt, however, when the temperature is raised. This is likely due to increased vibrational amplitudes combined with the confining effect of the Gr film.