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Title: Structural properties of the multilayer graphene/4H-SiC(0001) system as determined by surface x-ray diffraction

Abstract

We present a structural analysis of the multilayer graphene/4HSiC(0001) system using surface x-ray reflectivity. We show that graphene films grown on the C-terminated (0001) surface have a graphene-substrate bond length that is very short (1.62 A). The measured distance rules out a weak van der Waals interaction to the substrate and instead indicates a strong bond between the first graphene layer and the bulk as predicted by ab initio calculations. The measurements also indicate that multilayer graphene grows in a near turbostratic mode on this surface. This result may explain the lack of a broken graphene symmetry inferred from conduction measurements on this system [C. Berger et al., Science 312, 1191 (2006)].

Authors:
; ; ; ; ; ; ; ;  [1];  [2]
  1. Georgia Institute of Technology, Atlanta, Georgia 30332-0430 (United States)
  2. (United States) and Institut Neel, Boite Postale 166, 38042 Grenoble Cedex (France)
Publication Date:
OSTI Identifier:
20951516
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 75; Journal Issue: 21; Other Information: DOI: 10.1103/PhysRevB.75.214109; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BOND LENGTHS; GRAPHITE; HYDROGEN 4; INTERFACES; LAYERS; REFLECTIVITY; ROUGHNESS; SILICON COMPOUNDS; STACKING FAULTS; SUBSTRATES; SURFACES; THIN FILMS; VAN DER WAALS FORCES; X-RAY DIFFRACTION

Citation Formats

Hass, J., Feng, R., Millan-Otoya, J. E., Li, X., Sprinkle, M., First, P. N., Heer, W. A. de, Conrad, E. H., Berger, C., and Georgia Institute of Technology, Atlanta, Georgia 30332-0430. Structural properties of the multilayer graphene/4H-SiC(0001) system as determined by surface x-ray diffraction. United States: N. p., 2007. Web. doi:10.1103/PHYSREVB.75.214109.
Hass, J., Feng, R., Millan-Otoya, J. E., Li, X., Sprinkle, M., First, P. N., Heer, W. A. de, Conrad, E. H., Berger, C., & Georgia Institute of Technology, Atlanta, Georgia 30332-0430. Structural properties of the multilayer graphene/4H-SiC(0001) system as determined by surface x-ray diffraction. United States. doi:10.1103/PHYSREVB.75.214109.
Hass, J., Feng, R., Millan-Otoya, J. E., Li, X., Sprinkle, M., First, P. N., Heer, W. A. de, Conrad, E. H., Berger, C., and Georgia Institute of Technology, Atlanta, Georgia 30332-0430. Fri . "Structural properties of the multilayer graphene/4H-SiC(0001) system as determined by surface x-ray diffraction". United States. doi:10.1103/PHYSREVB.75.214109.
@article{osti_20951516,
title = {Structural properties of the multilayer graphene/4H-SiC(0001) system as determined by surface x-ray diffraction},
author = {Hass, J. and Feng, R. and Millan-Otoya, J. E. and Li, X. and Sprinkle, M. and First, P. N. and Heer, W. A. de and Conrad, E. H. and Berger, C. and Georgia Institute of Technology, Atlanta, Georgia 30332-0430},
abstractNote = {We present a structural analysis of the multilayer graphene/4HSiC(0001) system using surface x-ray reflectivity. We show that graphene films grown on the C-terminated (0001) surface have a graphene-substrate bond length that is very short (1.62 A). The measured distance rules out a weak van der Waals interaction to the substrate and instead indicates a strong bond between the first graphene layer and the bulk as predicted by ab initio calculations. The measurements also indicate that multilayer graphene grows in a near turbostratic mode on this surface. This result may explain the lack of a broken graphene symmetry inferred from conduction measurements on this system [C. Berger et al., Science 312, 1191 (2006)].},
doi = {10.1103/PHYSREVB.75.214109},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 21,
volume = 75,
place = {United States},
year = {Fri Jun 01 00:00:00 EDT 2007},
month = {Fri Jun 01 00:00:00 EDT 2007}
}
  • The principal structural defects in graphene multilayers synthesized on the carbon-terminated face of a 4H-SiC (0001{sup ¯}) substrate were investigated using the high-resolution transmission electron microscopy. The analyzed systems include a wide variety of defected structures such as edge dislocations, rotational multilayers, and grain boundaries. It was shown that graphene layers are composed of grains of the size of several nanometres or larger; they differ in a relative rotation by large angles, close to 30°. The structure of graphene multilayers results from the synthesis on a SiC (0001{sup ¯}) surface, which proceeds via intensive nucleation of new graphene layers thatmore » coalesce under various angles creating an immense orientational disorder. Structural defects are associated with a built-in strain resulting from a lattice mismatch between the SiC substrate and the graphene layers. The density functional theory data show that the high-angular disorder of AB stacked bi-layers is not restoring the hexagonal symmetry of the lattice.« less
  • Efficient control of intercalation of epitaxial graphene by specific elements is a way to change properties of the graphene. Results of several experimental techniques, such as X-ray photoelectron spectroscopy, micro-Raman mapping, reflectivity, attenuated total reflection, X-ray diffraction, and X-ray reflectometry, gave a new insight into the intercalation of oxygen in the epitaxial graphene grown on 4H-SiC(0001). These results confirmed that oxygen intercalation decouples the graphene buffer layer from the 4H-SiC surface and converts it into the graphene layer. However, in contrast to the hydrogen intercalation, oxygen does not intercalate between carbon planes (in the case of few layer graphene) andmore » the interlayer spacing stays constant at the level of 3.35–3.32 Å. Moreover, X-ray reflectometry showed the presence of an oxide layer having the thickness of about 0.8 Å underneath the graphene layers. Apart from the formation of the nonuniform thin oxide layer, generation of defects in graphene caused by oxygen was also evidenced. Last but not least, water islands underneath defected graphene regions in both intercalated and non-intercalated samples were most probably revealed. These water islands are formed in the case of all the samples stored under ambient laboratory conditions. Water islands can be removed from underneath the few layer graphene stacks by relevant thermal treatment or by UV illumination.« less
  • Large-area graphene film doped with hetero-atoms is of great interest for a wide spectrum of nanoelectronics applications, such as field effect devices, super capacitors, fuel cells among many others. Here, we report the structural and electronic properties of nitrogen doped multilayer graphene on 4H-SiC (0001). The incorporation of nitrogen during the growth causes an increase in the D band on the Raman signature indicating that the nitrogen is creating defects. The analysis of micro-Raman mapping of G, D, 2D bands shows a predominantly trilayer graphene with a D band inherent to doping and inhomogeneous dopant distribution at the step edges.more » Ultraviolet photoelectron spectroscopy (UPS) indicates an n type work function (WF) of 4.1 eV. In addition, a top gate FET device was fabricated showing n-type I-V characteristic after the desorption of oxygen with high electron and holes mobilities.« less
  • A Si{sub 3}N{sub 4} passivation layer has been successfully grown on the 4H-SiC (0001) surface by direct atomic source nitridation at various substrate temperatures. In situ x-ray photoelectron spectroscopy measurements show that higher substrate temperature leads to higher nitridation rate and good crystallinity of the passivation layer. A thin oxynitride layer on the top of the Si{sub 3}N{sub 4} was observed due to the residual O in the vacuum system, but was decomposed during annealing. In the meantime, excess C was found to be effectively removed by the reactive atomic N source.
  • Structural investigations of hydrogenated epitaxial graphene grown on SiC(0001) are presented. It is shown that hydrogen plays a dual role. In addition to contributing to the well-known removal of the buffer layer, it goes between the graphene planes, resulting in an increase of the interlayer spacing to 3.6 Å–3.8 Å. It is explained by the intercalation of molecular hydrogen between carbon planes, which is followed by H{sub 2} dissociation, resulting in negatively charged hydrogen atoms trapped between the graphene layers, with some addition of covalent bonding to carbon atoms. Negatively charged hydrogen may be responsible for p-doping observed in hydrogenated multilayer graphene.