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Multiscale investigation of graphene layers on 6H-SiC(000-1).

Tiberj A, Huntzinger JR, Camassel J, Hiebel F, Mahmood A, Mallet P, Naud C, Veuillen JY - Nanoscale Res Lett (2011)

Bottom Line: At the same scale, electron diffraction reveals a significant rotational disorder between the first graphene layer and the SiC surface, although well-defined preferred orientations exist.This is confirmed at the nanometer scale by scanning tunneling microscopy (STM).The most striking result is that the FLGs experience a strong compressive stress that is seldom observed for graphene grown on the C face of SiC substrates.

View Article: PubMed Central - HTML - PubMed

Affiliation: Groupe d'Etude des Semiconducteurs, UMR5650 CNRS-Université Montpellier II, cc074, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France. Antoine.Tiberj@univ-montp2.fr.

ABSTRACT
In this article, a multiscale investigation of few graphene layers grown on 6H-SiC(000-1) under ultrahigh vacuum (UHV) conditions is presented. At 100-μm scale, the authors show that the UHV growth yields few layer graphene (FLG) with an average thickness given by Auger spectroscopy between 1 and 2 graphene planes. At the same scale, electron diffraction reveals a significant rotational disorder between the first graphene layer and the SiC surface, although well-defined preferred orientations exist. This is confirmed at the nanometer scale by scanning tunneling microscopy (STM). Finally, STM (at the nm scale) and Raman spectroscopy (at the μm scale) show that the FLG stacking is turbostratic, and that the domain size of the crystallites ranges from 10 to 100 nm. The most striking result is that the FLGs experience a strong compressive stress that is seldom observed for graphene grown on the C face of SiC substrates.

No MeSH data available.


Related in: MedlinePlus

LEED patterns of a 6H-SiC(000-1) sample after graphitization. The circles indicate the (1 × 1) SiC spots, the white arrows the (3 × 3) SiC spots, and the rose arrows point to faint SiC(2 × 2)C spots. The dashed (quarter) circle shows the ringlike pattern of graphene. The modulated intensity of FLGs signal corresponds to the distribution of rotation angles for the first graphene layer compared to the SiC surface with some preferential orientations (the brightest spots).
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Figure 1: LEED patterns of a 6H-SiC(000-1) sample after graphitization. The circles indicate the (1 × 1) SiC spots, the white arrows the (3 × 3) SiC spots, and the rose arrows point to faint SiC(2 × 2)C spots. The dashed (quarter) circle shows the ringlike pattern of graphene. The modulated intensity of FLGs signal corresponds to the distribution of rotation angles for the first graphene layer compared to the SiC surface with some preferential orientations (the brightest spots).

Mentions: The sample graphitization and first characterization (STM, LEED, and AES) were performed in situ under UHV conditions according to the procedure of ref. [18]. The surface of the 6H-SiC(000-1) sample (n doped, purchased from NovaSiC) was first cleaned by a 850°C annealing treatment under a Si flux. The usual SiC(3 × 3) reconstruction [16] was obtained by further heating at 950-1000°C. Graphitization of the surface was performed by annealing at increased power until a graphitic signal is detected by LEED. The typical diffraction patterns (shown in Figure 1) reveal both SiC(3 × 3) and SiC(2 × 2) spots indicated by arrows with SiC(1 × 1) spots being indicated by circles. The FLGs exhibit a ringlike LEED pattern with modulated intensity indicated by the dashed circle. It evidences a significant distribution of azimuthal disorientation for the first graphene plane compared to the SiC lattice. However, some preferential orientations exist, as shown by the more intense spots (at 30° and predominantly around 14°). AES performed on this sample gives an average coverage of the surface of 1 to 2 graphene layers.


Multiscale investigation of graphene layers on 6H-SiC(000-1).

Tiberj A, Huntzinger JR, Camassel J, Hiebel F, Mahmood A, Mallet P, Naud C, Veuillen JY - Nanoscale Res Lett (2011)

LEED patterns of a 6H-SiC(000-1) sample after graphitization. The circles indicate the (1 × 1) SiC spots, the white arrows the (3 × 3) SiC spots, and the rose arrows point to faint SiC(2 × 2)C spots. The dashed (quarter) circle shows the ringlike pattern of graphene. The modulated intensity of FLGs signal corresponds to the distribution of rotation angles for the first graphene layer compared to the SiC surface with some preferential orientations (the brightest spots).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211224&req=5

Figure 1: LEED patterns of a 6H-SiC(000-1) sample after graphitization. The circles indicate the (1 × 1) SiC spots, the white arrows the (3 × 3) SiC spots, and the rose arrows point to faint SiC(2 × 2)C spots. The dashed (quarter) circle shows the ringlike pattern of graphene. The modulated intensity of FLGs signal corresponds to the distribution of rotation angles for the first graphene layer compared to the SiC surface with some preferential orientations (the brightest spots).
Mentions: The sample graphitization and first characterization (STM, LEED, and AES) were performed in situ under UHV conditions according to the procedure of ref. [18]. The surface of the 6H-SiC(000-1) sample (n doped, purchased from NovaSiC) was first cleaned by a 850°C annealing treatment under a Si flux. The usual SiC(3 × 3) reconstruction [16] was obtained by further heating at 950-1000°C. Graphitization of the surface was performed by annealing at increased power until a graphitic signal is detected by LEED. The typical diffraction patterns (shown in Figure 1) reveal both SiC(3 × 3) and SiC(2 × 2) spots indicated by arrows with SiC(1 × 1) spots being indicated by circles. The FLGs exhibit a ringlike LEED pattern with modulated intensity indicated by the dashed circle. It evidences a significant distribution of azimuthal disorientation for the first graphene plane compared to the SiC lattice. However, some preferential orientations exist, as shown by the more intense spots (at 30° and predominantly around 14°). AES performed on this sample gives an average coverage of the surface of 1 to 2 graphene layers.

Bottom Line: At the same scale, electron diffraction reveals a significant rotational disorder between the first graphene layer and the SiC surface, although well-defined preferred orientations exist.This is confirmed at the nanometer scale by scanning tunneling microscopy (STM).The most striking result is that the FLGs experience a strong compressive stress that is seldom observed for graphene grown on the C face of SiC substrates.

View Article: PubMed Central - HTML - PubMed

Affiliation: Groupe d'Etude des Semiconducteurs, UMR5650 CNRS-Université Montpellier II, cc074, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France. Antoine.Tiberj@univ-montp2.fr.

ABSTRACT
In this article, a multiscale investigation of few graphene layers grown on 6H-SiC(000-1) under ultrahigh vacuum (UHV) conditions is presented. At 100-μm scale, the authors show that the UHV growth yields few layer graphene (FLG) with an average thickness given by Auger spectroscopy between 1 and 2 graphene planes. At the same scale, electron diffraction reveals a significant rotational disorder between the first graphene layer and the SiC surface, although well-defined preferred orientations exist. This is confirmed at the nanometer scale by scanning tunneling microscopy (STM). Finally, STM (at the nm scale) and Raman spectroscopy (at the μm scale) show that the FLG stacking is turbostratic, and that the domain size of the crystallites ranges from 10 to 100 nm. The most striking result is that the FLGs experience a strong compressive stress that is seldom observed for graphene grown on the C face of SiC substrates.

No MeSH data available.


Related in: MedlinePlus