title: Uniform Atomic Layer Deposition of Al2O3on Graphene by Reversible Hydrogen Plasma Functionalization.
abstract: A novel method to form ultrathin, uniform Al2O3layers 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 Al2O3films down to 8 nm in thickness. Hall measurements and Raman spectroscopy reveal that the hydrogen plasma functionalization is reversible upon Al2O3ALD 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 H2and O2plasma 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 Al2O3ALD.
authors.affiliation: Department of Applied Physics, Eindhoven University of Technology , P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
authors.forename: René H J
authors.initials: RH
authors.lastname: Vervuurt
authors.affiliation: Department of Applied Physics, Eindhoven University of Technology , P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
authors.forename: Bora
authors.initials: B
authors.lastname: Karasulu
authors.affiliation: Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands; Philips Innovation Labs, High Tech Campus 11, 5656 AE Eindhoven, The Netherlands.
authors.forename: Marcel A
authors.initials: MA
authors.lastname: Verheijen
authors.affiliation: Department of Applied Physics, Eindhoven University of Technology , P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
authors.forename: Wilhelmus Erwin M M
authors.initials: WE
authors.lastname: Kessels
authors.affiliation: Department of Applied Physics, Eindhoven University of Technology , P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
authors.forename: Ageeth A
authors.initials: AA
authors.lastname: Bol