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Impact of Atomic Oxygen on the Structure of Graphene Formed on Ir(111) and Pt(111)
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
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2011 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 19, 9568-9577 p.Article in journal (Refereed) Published
Abstract [en]

The effect of atomic oxygen adsorption on the structure and electronic properties of monolayer graphite (MG or graphene) grown on Pt(111) and Ir(111) has been studied using X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and scanning tunneling microscopy. For comparison, the adsorption of atomic oxygen on highly oriented pyrolytic graphite has been studied under the same conditions. Graphene oxidation predominantly occurs through the formation of epoxy groups and causes atomic-scale buckling of the graphene lattice, as evidenced by an sp(2)-to-sp(3) bonding transformation. The different parts of the graphene/metal moire superstructure show different oxidation dynamics, with the initial formation of epoxy groups in the more bonding "pores". Upon 0 adsorption, the nearest C neighbors of epoxy groups get engaged in a stronger bonding with the substrate. As a result, the pores of the graphene mesh become attracted and effectively pinned to the substrate by the 0 atoms. A limited intercalation of oxygen under graphene is also probable. Annealing of the samples after oxygen exposure only partially recovers the original graphene structure and results in the formation of a dense pattern of quasi-periodic, nanometer-sized holes. Both the selective oxidization and the hole formation can be exploited for selective functionalization or tuning of the electronic properties.

Place, publisher, year, edition, pages
2011. Vol. 115, no 19, 9568-9577 p.
National Category
Physical Sciences
URN: urn:nbn:se:uu:diva-154296DOI: 10.1021/jp111962kISI: 000290427400033OAI: oai:DiVA.org:uu-154296DiVA: diva2:419900
Available from: 2011-05-30 Created: 2011-05-30 Last updated: 2013-03-22Bibliographically approved
In thesis
1. Controlling Electronic and Geometrical Structure of Honeycomb-Lattice Materials Supported on Metal Substrates: Graphene and Hexagonal Boron Nitride
Open this publication in new window or tab >>Controlling Electronic and Geometrical Structure of Honeycomb-Lattice Materials Supported on Metal Substrates: Graphene and Hexagonal Boron Nitride
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present thesis is focused on various methods of controlling electronic and geometrical structure of two-dimensional overlayers adsorbed on metal surfaces exemplified by graphene and hexagonal boron nitride (h-BN) grown on transition metal (TM) substrates. Combining synchrotron-radiation-based spectroscopic and various microscopic techniques with in situ sample preparation, we are able to trace the evolution of overlayer electronic and geometrical properties in overlayer/substrate systems, as well as changes of interfacial interaction in the latter.It is shown that hydrogen uptake by graphene/TM substrate strongly depends on the interfacial interaction between substrate and graphene, and on the geometrical structure of graphene. An energy gap opening in the electronic structure of graphene on TM substrates upon patterned adsorption of atomic species is demonstrated for the case of atomic oxygen adsorption on graphene/TM’s (≥0.35 eV for graphene/Ir(111)). A non-uniform character of adsorption in this case – patterned adsorption of atomic oxygen on graphene/Ir(111) due to the graphene height modulation is verified. A moderate oxidation of graphene/Ir(111) is found largely reversible. Contrary, oxidation of h-BN/Ir(111) results in replacing nitrogen atoms in the h-BN lattice with oxygen and irreversible formation of the B2O3 oxide-like structure.     

Pronounced hole doping (p-doping) of graphene upon intercalation with active agents – halogens or halides – is demonstrated, the level of the doping is dependent on the agent electronegativity. Hole concentration in graphene on Ir(111) intercalated with Cl and Br/AlBr3 is as high as ~2×1013 cm-2 and ~9×1012 cm-2, respectively.    

Unusual periodic wavy structures are reported for h-BN and graphene grown on Fe(110) surface. The h-BN monolayer on Fe(110) is periodically corrugated in a wavy fashion with an astonishing degree of long-range order, periodicity of 2.6 nm, and the corrugation amplitude of ~0.8 Å. The wavy pattern results from a strong chemical bonding between h-BN and Fe in combination with a lattice mismatch in either [11 ̅1] or [111 ̅] direction of the Fe(110) surface. Two primary orientations of h-BN on Fe(110) can be observed corresponding to the possible directions of lattice match between h-BN and Fe(110).    

Chemical vapor deposition (CVD) formation of graphene on iron is a formidable task because of high carbon solubility in iron and pronounced reactivity of the latter, favoring iron carbide formation. However, growth of graphene on epitaxial iron films can be realized by CVD at relatively low temperatures, and the formation of carbides can be avoided in excess of the carbon-containing precursors. The resulting graphene monolayer creates a periodically corrugated pattern on Fe(110): it is modulated in one dimension forming long waves with a period of ~4 nm parallel to the [001] direction of the substrate, with an additional height modulation along the wave crests. The novel 1D templates based on h-BN and graphene adsorbed on iron can possibly find an application in 1D nanopatterning. The possibility for growing high-quality graphene on iron substrate can be useful for the low-cost industrial-scale graphene production.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 103 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1019
graphene, h-BN, electronic structure, adsorption, doping, nano-templates, PES, NEXAFS, LEEM, STM
National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
urn:nbn:se:uu:diva-194089 (URN)978-91-554-8598-6 (ISBN)
Public defence
2013-04-05, Häggsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Available from: 2013-03-13 Created: 2013-02-08 Last updated: 2013-03-22Bibliographically approved

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