Probing the Structure
and Chemistry of Perylenetetracarboxylic
Dianhydride on Graphene Before and After Atomic Layer Deposition of
Alumina
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Abstract
The superlative electronic properties of graphene suggest
its use
as the foundation of next-generation integrated circuits. However,
this application requires precise control of the interface between
graphene and other materials, especially the metal oxides that are
commonly used as gate dielectrics. Toward that end, organic seeding
layers have been empirically shown to seed ultrathin dielectric growth
on graphene via atomic layer deposition (ALD), although the underlying
chemical mechanisms and structural details of the molecule/dielectric
interface remain unknown. Here, confocal resonance Raman spectroscopy
is employed to quantify the structure and chemistry of monolayers
of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on graphene
before and after deposition of alumina with the ALD precursors trimethyl
aluminum (TMA) and water. Photoluminescence measurements provide further
insight into the details of the growth mechanism, including the transition
between layer-by-layer growth and island formation. Overall, these
results reveal that PTCDA is not consumed during ALD, thereby preserving
a well-defined and passivating organic interface between graphene
and deposited dielectric thin films