Abstract
Large scale tetraoctylammonium-assisted electrochemical transfer of graphene grown on single-crystalline Ir(1 1 1) films by chemical vapour deposition is reported. The transferred samples are characterized in air with optical microscopy, Raman spectroscopy and four point transport measurements, providing the sheet resistance and the Hall carrier concentration. In vacuum we apply low energy electron diffraction and photoelectron spectroscopy that indicate transferred large-scale single orientation graphene. Angular resolved photoemission reveals a Fermi surface and a Dirac point energy which are consistent with charge neutral graphene.
Highlights
Ultrathin two dimensional (2D) materials are expected to revolutionize materials science and technology [1,2,3]
A comparison with optical microscopy data for SiO2supported multilayer graphene transferred from Cu foil confirms the absence of multi-layer graphene
The sign of the Fermi level shift is the same as observed in photoemission experiments, where a significant Ohmic resistance induces a shift of the Fermi level, i.e. a net positive charge, which in turn produces an additional potential that the photoelectrons have to overcome
Summary
Ultrathin two dimensional (2D) materials are expected to revolutionize materials science and technology [1,2,3]. While dry transfer is promising on small scales [7], so far, wet transfer methods produce larger scale graphenes that are e.g. needed in conventional photoemission experiments. Photoemission from graphene [8,9,10,11,12] yields direct insight into the electronic structure and the measurement of relevant quantities like the Dirac energy and the Fermi velocity. The experiments on freestanding [13] and/or transferred [14, 15] samples pose more challenges due to the difficulty of producing large-scale films, and, up to date, most results found in literature are for micrometer-sized samples [8, 16, 17]
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