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Uniform Atomic Layer Deposition of Al2O3 on Graphene by Reversible Hydrogen Plasma Functionalization
journal contribution
posted on 2017-02-23, 00:00 authored by René
H. J. Vervuurt, Bora Karasulu, Marcel A. Verheijen, Wilhelmus (Erwin)
M. M. Kessels, Ageeth A. BolA novel
method to form ultrathin, uniform Al2O3 layers
on graphene using reversible hydrogen plasma functionalization
followed by atomic layer deposition (ALD) is presented. ALD on pristine
graphene is known to be a challenge due to the absence of dangling
bonds, leading to nonuniform film coverage. We show that hydrogen
plasma functionalization of graphene leads to uniform ALD of closed
Al2O3 films down to 8 nm in thickness. Hall
measurements and Raman spectroscopy reveal that the hydrogen plasma
functionalization is reversible upon Al2O3 ALD
and subsequent annealing at 400 °C and in this way does not deteriorate
the graphene’s charge carrier mobility. This is in contrast
with oxygen plasma functionalization, which can lead to a uniform
5 nm thick closed film, but which is not reversible and leads to a
reduction of the charge carrier mobility. Density functional theory
(DFT) calculations attribute the uniform growth on both H2 and O2 plasma functionalized graphene to the enhanced
adsorption of trimethylaluminum (TMA) on these surfaces. A DFT analysis
of the possible reaction pathways for TMA precursor adsorption on
hydrogenated graphene predicts a binding mechanism that cleans off
the hydrogen functionalities from the surface, which explains the
observed reversibility of the hydrogen plasma functionalization upon
Al2O3 ALD.
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Keywords
O 2 plasma functionalized grapheneUniform Atomic Layer DepositionAl 2 O 3 ALDlayer depositionform ultrathincharge carrier mobilityhydrogen plasma functionalizationAl 2 O 3uniform 5 nmReversible Hydrogen Plasma FunctionalizationRaman spectroscopybinding mechanismH 2reaction pathwaysuniform ALD8 nmhydrogen functionalitieshall measurementsAl 2 O 3 filmshydrogenated grapheneoxygen plasma functionalizationTMA precursor adsorptionuniform growthDFT analysisnonuniform film coverageuniform Al 2 O 3 layersnovel method
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