Abstract
Wave vector-resolved inverse photoelectron spectroscopy (IPES)measurements have been used to demonstrate that there is a large variationof interfacial charge transfer between the supporting substrate andgraphene. The results were obtained for graphene grown by chemical vapordeposition(CVD) on a range of dielectric or metallic substrates. Monolayer graphenegrown by CVD on monolayer BN(0001)/Ru(0001) exhibits strong chargetransfer from the substrate to graphene of 0.07(1) e- per carbon atom,evident from the filling of the π* band and displacement of the Fermilevel. Inversephotoelectron spectroscopy (IPES) measurements of CVD single layergraphene on Ru indicate a substrate-to-graphene charge transfer from thesubstrate of 0.06(1) e- per carbon atom, in agreement with reportedangle-resolved photoemission results. The IPES spectra of CVD single layergraphene onNi(polycystalline), and on Cu(polycystalline) indicate 0.03(1) e- percarbon atom charge transfer from Ni and Cu substrates. IPES measurementsindicate that single layer graphene on MgO(111) exhibit 0.02(1) e- percarbon atom charge is transferred from graphene to the MgO substrate.Additionally, IPES and photoemission data, when combined, along withcharging in the retarding potential vacuum diode geometry indicate thatsingle layer graphene/MgO(111) exhibits a band gap. These data demonstratethat IPES is one effective method for precise measurement ofsubstrate/graphene charge transfer and related electronic interactions, inpart because of the extreme surface sensitivity of the technique. Lookingto the future, comparison of graphene electronic structure on manysubstrates may suggest new strategies for extrinsic doping of graphene forcontrolled mobilities for device applications. The opening of a band gapcan be related to a reduction in symmetry from C6 to C3 or looking at itanother way, making the A and B site of graphene chemically inequivalent.Graphene is not simply chemically inert. We find that the photoemissionand inverse photoemission final states are better screened for dipolarmolecules, with a large intrinsic dipole of 10 Debyes, on gold than isobserved to be the case on graphene on copper, and this is evident in alarger highest occupied molecular orbital to lowest unoccupied molecularorbital gap.Work done with Lingmei Kong,1 Cameron Bjelkevig,2 Sneha Gaddam,2 Mi Zhou,2Young Hee Lee,3 Gang Hee Han,3 Hae Kyung Jeong,4 Ning Wu,1 ZhengzhengZhang,1 Jie Xiao,1 and Jeffry A. Kelber21) University of Nebraska-Â‐Lincoln2) University of North Texas.3) Sungkyunkwan University, Suwon, 440-Â‐746 Korea (ROK)4) Daegu University, Gyeongsan, 712-Â‐714 Korea (ROK)
