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Instruments / Technical Area	Publication Details	Published
I09-Surface and Interface Structural Analysis	Selective hydrogenation of graphene on Ir(111): an X-ray standing wave study Claus F. P. Kastorp , David A. Duncan , Anders l. Jørgensen , Martha Scheffler , John D. Thrower , Tien-Lin Lee , Liv Hornekaer , Richard Balog Faraday Discussions 141 DOI: 10.1039/D1FD00122A Diamond Proposal Number(s): [16243] Open Access Show Abstract ▼ Abstract: A combined high resolution X-ray photoelectron spectroscopy and X-ray standing wave study into the adsorption structure of hydrogenated graphene on Ir(111) is presented. By exploiting the unique absorption profiles and significant modulations in signal intensity found within the X-ray standing wave results, we refine the fitting of the C 1s X-ray photoelectron spectra, allowing us to disentangle the contributions from hydrogenation of graphene in different high-symmetry regions of the moiré supercell. We clearly demonstrate that hydrogenation in the FCC regions results in the formation of a graphane-like structure, giving a standalone component that is separated from the component assigned to the similar structure in the HCP regions. The contribution from dimer structures in the ATOP regions is found to be minor or negligible. This is in contrast to the previous findings where a dimer structure was assumed to contribute significantly to the sp3 part of the C 1s spectra. The corrugation of the remaining pristine parts of the H-graphene is shown to increase with the H coverage, reflecting an increasing number and size of pinning centers of the graphene to the Ir(111) substrate with increasing H exposure.	May 2022
I09-Surface and Interface Structural Analysis	Growth and electronic properties of bi- and trilayer graphene on Ir(111) Claus F. P. Kastorp , David A. Duncan , Martha Scheffler , John D. Thrower , Anders L. Jørgensen , Hadeel Hussain , Tien-Lin Lee , Liv Hornekaer , Richard Balog Nanoscale 353 DOI: 10.1039/D0NR04788K Diamond Proposal Number(s): [16243] Open Access Show Abstract ▼ Abstract: Interesting electronic properties arise in vertically stacked graphene sheets, some of which can be controlled by mutual orientation of the adjacent layers. In this study, we investigate the MBE grown multilayer graphene on Ir(111) by means of STM, LEED and XPS and we examine the influence of the substrate on the geometric and electronic properties of bilayer graphene by employing XSW and ARPES measurements. We find that the MBE method does not limit the growth to two graphene layers and that the wrinkles, which arise through extended carbon deposition, play a crucial role in the multilayer growth. We also find that the bilayer and trilayer graphene sheets have graphitic-like properties in terms of the separation between the two layers and their stacking. The presence of the iridium substrate imposes a periodic potential induced by the moiré pattern that was found to lead to the formation of replica bands and minigaps in bilayer graphene. From tight-binding fits to our ARPES data we find that band renormalization takes place in multilayer graphene due to a weaker coupling of the upper-most graphene layer to the iridium substrate.	Sep 2020
I09-Surface and Interface Structural Analysis	Chemically-resolved determination of hydrogenated graphene-substrate interaction Anders L. Jørgensen , David A. Duncan , Claus F. P. Kastorp , Line Kyhl , Zeyuan Tang , Albert Bruix , Mie Andersen , Bjork Hammer , Tien-Lin Lee , Liv Hornekaer , Richard Balog Physical Chemistry Chemical Physics DOI: 10.1039/C9CP02059D Diamond Proposal Number(s): [16243] Show Abstract ▼ Abstract: Functionalization of graphene on Ir(111) is a promising route to modify graphene by chemical means in a controlled fashion at the nanoscale. Yet, the nature of such functionalized sp3 nanodots remains unknown. Density functional theory (DFT) calculations alone cannot differentiate between two plausible structures, namely true graphane and substrate stabilized graphane-like nanodots. These two structures, however, interact dramatically differently with the underlying substrate. Discriminating which type of nanodots forms on the surface is thus of paramount importance for the applications of such prepared nanostructures. By comparing X-ray standing wave measurements against theoretical model structures obtained by DFT calculations we are able to exclude the formation of true graphane nanodots and clearly show the formation graphane-like nanodots.	Jun 2019

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