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WOS: 000349657600001, There exist many reports on functionalisation of graphene on a non-spatially resolved scale; this report concentrates on reviewing atomic-scale interactions of functionalising agents, i.e. on the electronic behaviour of single atoms, which are introduced as adatoms or lattice site impurities for the purpose of external doping and dosing to achieve bandgap engineering and electrical contacting of graphene; it also reviews the associated defects. Emphasis is put on visualisation of such interactions by advanced imaging in conjunction with localised spectroscopy techniques. Whereas the existing literature describing the development of such techniques in the application to graphene warrants a review in its own right, here the authors focus on observations, with modelling support, of the interaction phenomena themselves and not on the evaluation of measurements by such techniques. Atomic resolution transmission electron microscopy (TEM) combined with electron energy loss spectroscopy (EELS) in imaging and scanning mode, as well as scanning tunnelling microscopy (STM) are the most frequently applied techniques in aid of revealing topography and defect assisted interactions of graphene with foreign atoms and molecules. Electron-probe based investigations additionally lead to electron beam assisted interactions of foreign species with graphene. The graphene metal interaction observed in a transmission electron microscope is a prevalent example of how reactions occurring between metals and graphene can be emphasised and thereby assessed: metal-mediated etching of graphene has proven to be a common phenomenon after metal dosing, e.g. to fabricate electrical contacts. The review reports furthermore on investigations revealing atomic position, bonding and dynamics of non-metal p- and n-dopants as well as on revealing the functionalisation of graphene via molecular self-assembly, intercalation and nano-sculpting. Literature till the end of 2013/begin of 2014 is reviewed., Engineering and Physical Sciences Research Council [EP/I008144/1]

WOS: 000356554500028, Two-dimensional (2D) layers like graphene are subject to long-wavelength fluctuations that manifest themselves as strong height fluctuations (ripples). In order to control the ripples, their relationship with external strain needs to be established. We therefore perform molecular dynamics (MD) of suspended graphene, by the use of a newly developed force field model (MMP) that we prove to be extremely accurate for both C Diamond and Graphene. The MMP potential successfully reproduces the energy of the a-bonds in both sp(3) and sp(2) configuration. Our MD simulations and experimental electron microscopy analysis reveal that ordered and static ripples form spontaneously as a direct response to external pressure. Furthermore the morphology of graphene and strain response of the crystal bonds differ depending on the particular directions where external pressure is present. Different regions of the strained graphene sheet are then investigated by tight-binding. Localised bandgap opening is reported for specific strain combinations, which also results in particular signatures in the phonon spectrum. Such controllable morphological changes can therefore provide a means to practically control and tune the electronic and transport properties of graphene for applications as optoelectronic and nanoelectromechanical devices. (C) 2015 The Authors. Published by Elsevier Ltd., UK Engineering and Physical Sciences Research Council (EPSRC); Engineering and Physical Sciences Research Council [EP/H01182X/1], We are indebted to Dr. Stephan Birner of nextnano GmbH for his help with the modification needed of the Tight Binding routines in the nextnano source code. We are also grateful to Prof S. Clark of Durham University (UK) and Prof R.J. Young FRS (University of Manchester) for valuable discussions. We like to thank the UK Engineering and Physical Sciences Research Council (EPSRC) for Doctoral Prize Fellowship. We would also like to acknowledge Dr. Brian May CBE, of the band Queen, for kindly granting us permission to use the song Under Pressure (Queen and David Bowie, 1981) as soundtrack for our molecular dynamics video (Video S1). Due to copyright reasons the song was not used.

WOS: 000365464800090, PubMed ID: 26446310, A combination of scanning transmission electron microscopy, electron energy loss spectroscopy, and ab initio calculations is used to describe the electronic structure modifications incurred by free-standing graphene through two types of single-atom doping. The N K and C K electron energy loss transitions show the presence of pi* bonding states, which are highly localized around the N dopant. In contrast, the B K transition of a single B dopant atom shows an unusual broad asymmetric peak which is the result of delocalized pi* states away from the B dopant. The asymmetry of the B K toward higher energies is attributed to highly localized sigma* antibonding states. These experimental observations are then interpreted as direct fingerprints of the expected p- and n-type behavior of graphene doped in this fashion, through careful comparison with density functional theory calculations., Engineering and Physical Sciences Research Council (EPSRC); Engineering and Physical Sciences Research Council [EP/I008144/1], SuperSTEM is the U.K. National Facility for Aberration-Corrected STEM, supported by the Engineering and Physical Sciences Research Council (EPSRC). T.P.H. would like to thank the EPSRC for the Doctoral Prize Fellowship which funded this research in part. Computational work was undertaken using the advanced research computing (ARC1 and ARC2) HPC facilities at The University of Leeds, which provided access to Accelrys Materials Studio.

WOS: 000341914100007, PubMed ID: 25259987, We demonstrate that 60-keV electron irradiation drives the diffusion of threefold-coordinated Si dopants in graphene by one lattice site at a time. First principles simulations reveal that each step is caused by an electron impact on a C atom next to the dopant. Although the atomic motion happens below our experimental time resolution, stochastic analysis of 38 such lattice jumps reveals a probability for their occurrence in a good agreement with the simulations. Conversions from three- to fourfold coordinated dopant structures and the subsequent reverse process are significantly less likely than the direct bond inversion. Our results thus provide a model of nondestructive and atomically precise structural modification and detection for two-dimensional materials., Vienna Scientific Cluster; CSC Finland Ltd.; Austrian Science Fund (FWF) [M 1497-N19]; Finnish Cultural Foundation; Walter Ahlstrom Foundation; FWF [M 1481-N20, P25721-N20]; University of Helsinki Funds; European Research Council (ERC) [336453-PICOMAT]; Engineering and Physical Sciences Research Council (EPSRC) [EP/I008144/1]; Engineering and Physical Sciences Research Council [EP/I008144/1], We thank the Vienna Scientific Cluster and CSC Finland Ltd. for extensive grants of computational resources, and Ask Hjorth Larsen for help setting up the LCAO calculations. T. S. was supported by the Austrian Science Fund (FWF) through Grant No. M 1497-N19, by the Finnish Cultural Foundation, and by the Walter Ahlstrom Foundation. J. K. was supported by the FWF via Grant No. M 1481-N20, and by the University of Helsinki Funds. J. C. M. and C. M. acknowledge support from the FWF Project No. P25721-N20 and the European Research Council (ERC) Project No. 336453-PICOMAT. SuperSTEM is the UK National Facility for Aberration-Corrected STEM, supported by the Engineering and Physical Sciences Research Council (EPSRC), who also supported R. Z. and U. B. via Grant No. EP/I008144/1.