Graphene/Substrate Charge Transfer Characterized by Inverse Photoelectron Spectroscopy

Abstract

Wave vector-resolved inverse photoelectron spectroscopy (IPES) measurements demonstrate that there is a large variation of interfacial charge transfer for graphene grown by chemical vapor deposition (CVD) on a range of dielectric or metallic substrates. Monolayer graphene grown by CVD on monolayer BN(0001)/Ru(0001) exhibits strong charge transfer from the substrate to graphene of 0.07(1) e− per carbon atom, as manifested by filling of the π* band and displacement of the Fermi level. IPES measurements of CVD single layer graphene on Ru indicate a substrate-to-graphene charge transfer from the substrate of 0.06(1) e− per carbon atom, in agreement with reported angle-resolved photoemission results. The IPES spectra of CVD single layer graphene on Ni(poly) and on Cu(poly) indicate 0.03(1) e− per carbon atom charge transfer from Ni and Cu substrates. Single layer graphene has also been grown by free radical-assisted CVD on MgO(111), resulting in a layer of graphene and an oxidized carbon interfacial layer between the graphene and the substrate. IPES measurements indicate that 0.02(1) e− per carbon atom charge is transferred from graphene to the MgO substrate. Additionally, IPES and photoemission data indicate that single layer graphene/MgO(111) exhibits a band gap. These data demonstrate that IPES is an effective method for precise measurement of substrate/graphene charge transfer and related electronic interactions, in part because of the extreme surface sensitivity of the technique, and suggest new strategies for extrinsic doping of graphene for controlled mobilities for device applications.

Two-dimensional andπplasmon spectra in pristine and doped graphene

“…The dispersion curve obtained by solving (26) and using the complete response function (23), including all allowed intraand interband transitions, corresponds to the one published in Ref. 17, and is presented by a green dashed line in Fig.…”

“…The response function (23) includes all possible intra-and interband transitions between the π and π * bands. For example, the s = s terms represent intraband transitions where for negative doping (E F < 0) only the s = s = −1 term contributes, while for positive doping (E F > 0) only the s = s = 1 term contributes.…”

“…Assuming that the overlap matrix elements |F 11 (K,K )| 2 are equal to one, and keeping only the s = s = 1 term in the response function (23), it becomes…”

“…Doping can be achieved in various ways 22 and for different reasons, many of them related to the applications in electronics, e.g., by opening the gap at the Dirac point. Sometimes doping arises from the charge transfer from the substrate, 23 or is combined with the electrostatic field tuning, 24 where electrons are electrostatically injected into a graphene layer on the field-effect transistor (FET) principle. In this latter case the bands near the Dirac point do not change but the Fermi energy moves to the conduction band.…”

Modification of electronic surface states by graphene islands on Cu(111)

“…13 Recently, the surface states and electronic structure of graphene on a number of metal substrates have been studied using photoemission spectroscopy. [14][15][16][17] Scanning tunneling microscopy (STM) and spectroscopy (STS) studies provide a complementary viewpoint as a local probe sensitive to both occupied and unoccupied electronic states. In these experiments local topographical images provide structural information of measured sites, and local spectroscopy avoids the complexity of aggregated rotational domains.…”