Early stage of CVD graphene synthesis on Ge(001) substrate
2018
In this work we shed light on the early stage of the chemical vapor deposition of graphene on Ge(001)
surfaces. By a combined use of μ-Raman and x-ray photoelectron spectroscopies, and scanning tunneling
microscopy and spectroscopy, we were able to individuate a carbon precursor phase to graphene
nucleation which coexists with small graphene domains. This precursor phase is made of C aggregates
with different size, shape and local ordering which are not fully sp2 hybridized. In some atomic size
regions these aggregates show a linear arrangement of atoms as well as the first signature of the
hexagonal structure of graphene. The carbon precursor phase evolves in graphene domains through an
ordering process, associated to a re-arrangement of the Ge surface morphology. This surface structuring
represents the embryo stage of the hills-and-valleys faceting featured by the Ge(001) surface for longer
deposition times, when the graphene domains coalesce to form a single layer graphene film.
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