Strong metal adatom-substrate interaction of Gd and Fe with graphene.
ABSTRACT Graphene is a unique 2D system of confined electrons with an unusual electronic structure of two inverted Dirac cones touching at a single point, with high electron mobility and promising microelectronics applications. The clean system has been studied extensively, but metal adsorption studies in controlled experiments have been limited; such experiments are important to grow uniform metallic films, metal contacts, carrier doping, etc. Two non-free-electron-like metals (rare earth Gd and transition metal Fe) were grown epitaxially on graphene as a function of temperature T and coverage θ. By measuring the nucleated island density and its variation with growth conditions, information about the metal-graphene interaction (terrace diffusion, detachment energy) is extracted. The nucleated island densities at room temperature (RT) are stable and do not coarsen, at least up to 400 °C, which shows an unusually strong metal-graphene bond; most likely it is a result of C atom rebonding from the pure graphene sp(2) C-C configuration to one of lower energy.
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ABSTRACT: There is a tunable band gap in ABC-stacked few-layer graphene (FLG) via applying a vertical electric field, but the operation of FLG-based field effect transistor (FET) requires two gates to create a band gap and tune channel's conductance individually. Using first principle calculations, we propose an alternative scheme to open a band gap in ABC-stacked FLG namely via single-side adsorption. The band gap is generally proportional to the charge transfer density. The capability to open a band gap of metal adsorption decreases in this order: K/Al > Cu/Ag/Au > Pt. Moreover, we find that even the band gap of ABA-stacked FLG can be opened if the bond symmetry is broken. Finally, a single-gated FET based on Cu-adsorbed ABC-stacked trilayer graphene is simulated. A clear transmission gap is observed, which is comparable with the band gap. This renders metal-adsorbed FLG a promising channel in a single-gated FET device.Scientific Reports 05/2013; 3:1794.