We show that for metal/graphene/dielectric sandwich structures, charge doping in graphene depends on both the work functions of the metal and the dielectric. Using C-1s core level photoemission spectroscopy we determine the charge doping in graphene for one-sided metal contacts as well as for sandwich structures that are commonly used in graphene devices. The measured Fermi-level shifts are in good agreement with a model that predicts that the difference in charge doping for graphene on a metal compared to graphene sandwiched between a metal and dielectric is given by ΔEF ≈ 0.44 × √(Φmetal − Φdielectric)

Integration of graphene with other materials by direct growth, i.e., not using mechanical transfer procedures, is investigated on the example of metal/graphene/dielectric heterostructures. Such structures may become useful in spintronics applications using graphene as a spin-filter. Here, we systematically discuss the optimization of synthesis procedures for every layer of the heterostructure and characterize the material by imaging and diffraction methods. 300 nm thick contiguous (111) Ni-films are grown by physical vapor deposition on YSZ(111) or Al2O3(0001) substrates. Subsequently, chemical vapor deposition growth of graphene in ultra-high vacuum (UHV) is compared to tube-furnace synthesis. Only under UHV conditions, monolayer graphene in registry with Ni(111) has been obtained. In the tube furnace, mono- and bilayer graphene is obtained at growth temperatures of ∼800 °C, while at 900 °C, non-uniform thick graphene multilayers are formed. Y2O3 films grown by reactive molecular beam epitaxy in UHV covers the graphene/Ni(111) surface uniformly. Annealing to 500 °C results in crystallization of the yttria with a (111) surface orientation.

Integrating graphene into nanoelectronic device structure requires interfacing graphene with high-κ dielectric materials. However, the dewetting and thermal instability of dielectric layers on top of graphene makes fabricating a pinhole-free, uniform, and conformal graphene/dielectric interface challenging. Here, we demonstrate that an ultrathin layer of high-κ dielectric material Y2O3 acts as an effective seeding layer for atomic layer deposition of Al2O3 on graphene. Whereas identical Al2O3 depositions lead to discontinuous film on bare graphene, the Y2O3 seeding layer yields uniform and conformal films. The morphology of the Al2O3 film is characterized by atomic force microscopy and transmission electron microscopy. C-1s X-ray photoemission spectroscopy indicates that the underlying graphene remains intact following Y2O3 seed and Al2O3 deposition. Finally, photoemission measurements of the graphene/SiO2/Si, Y2O3/graphene/SiO2, and Al2O3/Y2O3/graphene/SiO2 interfaces indicate n-type doping of graphene with different doping levels due to charge transfer at the interfaces.

Graphene, grown by chemical vapor deposition, is transferred onto Nb-doped SrTiO3(001) surface and the interface properties are characterized by scanning tunneling microscopy and photoemission spectroscopy. Charge doping of graphene changes from n- to p-type with vacuum annealing and correspondingly opposite space charge regions are observed in SrTiO3 substrate. Formation of an ordered surface reconstruction of the SrTiO3 substrate underneath the graphene is observed. The surface restructuring can be measured in scanning tunneling microscopy because the graphene closely follows to the substrate topography. This causes at the atomic-level a wavy graphene morphology on the SrTiO3 (001)-c(6 × 2) surface reconstruction. Prolonged high temperature (above 700 °C) vacuum annealing causes formation of hexagonal holes with ‘armchair’ edges in the graphene and an eventual disappearance of the graphene. Etching of the graphene is assumed to be caused by reaction with released substrate oxygen.

Transition metal dichalcogenides exhibit spin–orbit split bands at the K‐point that become spin polarized for broken crystal inversion symmetry. This enables simultaneous manipulation of valley and spin degrees of freedom. While the inversion symmetry is broken for monolayers, we show here that spin polarization of the MoS2 surface may also be obtained by interfacing it with graphene, which induces a space charge region in the surface of MoS2. Polarization induced symmetry breaking in the potential gradient of the space charge is considered to be responsible for the observed spin polarization. In addition to spin polarization we also observe a renormalization of the valence band maximum (VBM) upon interfacing of MoS2 with graphene. The energy difference between the VBM at the Γ‐point and K‐point shifts by ∼150 meV between the clean and graphene covered surface. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)