Strong localization in weakly disordered epitaxial graphene

Surface Transport Properties of Pb-Intercalated Graphene

“…The Anderson temperature for the fit shown in Figure 5e is T 0 = 2.5 × 10 5 K, thus for quasi charge neutral graphene correlation lengths of 50 nm results in fair agreement with the average size of the intercalated areas shown in Figure 3. Similar localization effects were reported for weakly hydrogenated graphene [57,58].…”

Adsorption and Reaction of PbPc on Hydrogenated Epitaxial Graphene

“…A much stronger impact toward transport is found if chemisorbed H atoms are decorating the topmost graphene layer: Atomic hydrogen is forming strong bonds with a binding energy in the range of 1 eV (with respect to atomic H in the gas phase; see also Table ). Thereby, the sublattice symmetry is broken by strong local bending coming along with a metal insulator transition for coverages below 1% of a monolayer H. ,,, Accordingly, in our surface transport study an exponential increase of the resistivity upon the hydrogenation of MLG is found, as shown in Figure b. The resistivity increases by 2 orders of magnitude for an ultralow coverage of only half a percent of an monolayer and underlines the high sensitivity of our transport measurements.…”

“…Inset: I ( V ) curves for 0.07 and 0.47 ML of PbPc. (b) Relative change of resistivity of MLG upon adsorption of atomic hydrogen leading to strong localization . Inset: I ( V ) curves for a H coverage of 0.1% ML and 0.4% ML.…”

“…PbPc molecules were thermally evaporated onto the surfaces from a Knudsen cell by organic beam epitaxy at around 540 K and a substrate temperature of 300 K. Thereby, a monolayer (ML) refers to the molecular layer reported for a physical monolayer of flat-laying molecules adsorbed on MLG reported in ref . Atomic hydrogen was generated by thermal cracking of H 2 at 1700 °C and was also adsorbed on the graphene surface at 300 K. The coverage of the atomic hydrogen was deduced from detailed transport measurements outlined in a previous study . The H coverage is given with respect to surface atom density of graphene.…”

“…In particular, the transport properties of graphene are governed by the electronic bands; thus, both any change of the charge carrier concentrations and charge carrier mobility are captured by resistivity measurements. The pronounced metal–insulator transition measured upon adsorption of tiniest amounts of atomic hydrogen underlines the high sensitivity, , where the adsorption comes along with a strong lattice distortion due to the formation of sp 3 hybrids and modification of the band structure. − …”