Effect of oxygen adsorption on the local properties of epitaxial graphene on SiC (0001)

Mathieu, Claire; Lalmi, B.; Menteş, Tevfik Onur; Pallecchi, Emiliano; Locatelli, Andrea; Latil, Sylvain; Belkhou, Rachid; Ouerghi, Abdelkarim

doi:10.1103/physrevb.86.035435

Cited by 53 publications

(44 citation statements)

References 38 publications

(34 reference statements)

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“…E-mail: Thomas.Seyller@physik.tu-chemnitz.de (Thomas Seyller) dependent [4] and it has been observed that this is a direct consequence of the presence of the buffer layer [10]. In recent years, various elements such as gold [11], lithium [12], silicon [13], fluorine [14], germanium [15], oxygen [16][17][18][19] and hydrogen [10,[20][21][22][23] have been intercalated between the buffer layer and SiC(0001) in order to modify the interface.…”

Section: Introductionmentioning

confidence: 99%

“…From the observed π-plasmons in electron energy loss spectroscopy and graphene-related C1s core level components measured by x-ray photoelectron spectroscopy (XPS) they concluded that the buffer layer had been converted into graphene and that the latter remains undamaged by this process. Mathieu and coworkers [18] studied oxygen intercalation under MLG at higher temperature and lower oxygen pressure (T = 500 °C, p = 10 -4 torr, t = 3 h) and concluded that the buffer layer is partially decoupled from the substrate leading to bilayer graphene on an oxidized SiC(0001) surface. We have previously compared oxygen intercalation below the 6√3 buffer layer carried out under two different sets of conditions [17].…”

Section: Introductionmentioning

confidence: 99%

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Buffer layer free graphene on SiC(0001) via interface oxidation in water vapor

Ostler

Fromm

Koch

et al. 2014

Carbon

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Intercalation of various elements has become a popular technique to decouple the buffer layer of epitaxial graphene on SiC(0001) from the substrate. Among many other elements, oxygen can be used to passivate the SiC interface, causing the buffer layer to transform into graphene. Here, we study a gentle oxidation of the interface by annealing buffer layer and monolayer graphene samples in water vapor. X-ray photoelectron spectroscopy demonstrates the decoupling of the buffer layer from the SiC substrate. Raman spectroscopy is utilized to investigate a possible introduction of defects. Angle-resolved photoemission spectroscopy shows that the electronic structure of the water vapor treated samples. Low-energy electron microscopy (LEEM) measurements demonstrate that the decoupling takes place without changes in the surface morphology. The LEEM reflectivity spectra are discussed in terms of two different interpretations.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Buffer layer free graphene on SiC(0001) via interface oxidation in water vapor

Ostler

Fromm

Koch

et al. 2014

Carbon

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“…The local minimum in the LDOS indicated by the arrow is known to be to the position of the Dirac point (E D ) which is shifted with respect to the Fermi energy due to the strong charge transfer between graphene and the SiC substrate [17]. We find a Dirac Energy of E D ≈ -300 meV which implies a carrier concentration on the order of 10 13 cm -2 , characteristic of epitaxial monolayer graphene [18]. Carrier concentrations in this order are rather high in comparison to the ones measured for graphene produced by exfoliation or chemical vapor deposition (CVD) and can be reduced for instance with molecular doping [19].…”

Section: Cnrs-laboratoire De Photonique Et De Nanostructures (Lpn)mentioning

confidence: 94%

Epitaxial graphene on step bunching of a 6H-SiC(0001) substrate: Aromatic ring pattern and Van Hove singularities

Ridene

Wassmann

Pallecchi

et al. 2013

Applied Physics Letters

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We report scanning tunneling microscopy and spectroscopy investigation of graphene nanoribbons grown on an array of bunched steps of a 6H-SiC(0001) substrate. Our STM images of a GNR on a step terrace feature a (√3x√3)R30° pattern of aromatic rings which define our armchair nanoribbons. This is in agreement to a simulation based on density functional theory. As another signature of the one-dimensional electronic structure, in the corresponding STS spectra we find well developed, sharp Van Hove singularities.In the ongoing efforts to investigate the properties of graphene and related structures, graphene nanoribbons (GNRs) have attracted considerable attention. To a big part, this is due to the opening of an electronic band gap caused by the confinement of the electronic states in one dimension. The boundary conditions imposed by the edges, however, give rise to more phenomena than that. In this article, we address two of them, the formation of aromatic rings of delocalized π-electrons in the real space electron distribution and the appearance of Van Hove singularities (VHSs) in the local density of states (LDOS).Composed of a network of sp 2 hybridized carbon atoms, graphene can be thought of as a prototypic aromatic crystal. While three of the four valence electrons of each carbon atom are engaged in localized σ-bonds, the remaining one can form a π-bond with any of the three neighboring atoms. As long as nothing breaks the symmetry of the graphene crystal, all three options for the π-bond co-exist at the same time. When confined in narrow ribbons, however, considerations based on Clar's theory of the aromatic sextet have shown that certain π-bond configurations are preferred over others [1,2]. Depending on the edge configuration and the width of the ribbon, a distinct (√3x√3)R30° pattern of aromatic rings can form. As the states of the π-electrons lie close to the Fermi energy, this superstructure is detectable in STM measurements and has been observed near graphene edges [3]. Another effect of the one dimensional confinement of the electrons in GNRs is the appearance of divergences in the density of states (DOS) as a function of the energy, the so-called VHSs. They appear when a new sub-band in the electronic structure enters the bias window. Even though predicted theoretically, VHSs remain difficult to measure and when they are observed they are often suppressed by edge disorder [4,5].Contrary to other graphene growth methods, graphitization of SiC does not require a graphene transfer since SiC represents itself a suitable substrate for high power, high frequency, and opto-electronic devices [6]. The structure and electronic properties of graphene grown on SiC, however, strongly depend on the presence of steps on the substrate [6]. These steps, concentrated or bunched in narrow regions separated by larger atomically flat (0001) terraces, are known to be detrimental for the mobility of graphene. On the other hand, since the widths of the terraces are homogeneous to a high degree [7], they have proven to be us...

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“…In order to investigate the effect of Au deposition on the electronic properties, we have performed local ARPES experiments (µARPES). [9,17,24] and is attributed to doping from the buffer layer [6,7]. On the 2D µARPES map, recorded after Au deposition (Figure 4b), the energy difference between the Fermi level and the Dirac point is still 0.40 ± 0.02 eV.…”

Section: Au Intercalation In Epitaxial Graphene On Sic(0 0 0 1)mentioning

confidence: 99%

“…Furthermore, Riedl et al [16] have shown that hydrogen intercalation can induce such desired decoupling. More recently, it was demonstrated that the oxygen can partially decouple the buffer layer from the substrate and reduce the intrinsic electron doping [17]. Moreover, the intercalation of metal clusters or molecules between the graphene layers may serve to functionalize graphene.…”

Section: Introductionmentioning

confidence: 99%

Laterally Inhomogeneous Au Intercalation in Epitaxial Graphene on SiC(0 0 0 1): A Multimethod Electron Microscopy Study

Mathieu¹,

Menteş²,

Pallecchi³

et al. 2016

Recent Advances in Graphene Research

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Epitaxial graphene is of particular interest because of its tunable electronic structure.One important approach to tune the electronic properties of graphene relays on intercalating atomic species between graphene and the topmost silicon carbide layer.Here, we investigated the morphology and electronic structure of gold-intercalated epitaxial graphene using a multitechnique approach combining spectroscopic photoemission low-energy electron microscopy (SPELEEM) for chemical and structural characterization at mesoscopic length scale and with transmission electron microscopy (STEM) at the atomic level. Deposition of gold on ex situ prepared graphene on SiC(0 0 0 1) results in the partial intercalation of Au adatoms under graphene, with the formation of a buffer layer of variable thickness. Gold has also shown to aggregate in nanometer-sized clusters lying on top of the same graphene film. X-ray photo-emission electron microscopy measurements indicate that Au induces only small changes in the doping of the graphene layer, which does not develop a quasi free-standing behavior.

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Effect of oxygen adsorption on the local properties of epitaxial graphene on SiC (0001)

Cited by 53 publications

References 38 publications

Buffer layer free graphene on SiC(0001) via interface oxidation in water vapor

Buffer layer free graphene on SiC(0001) via interface oxidation in water vapor

Epitaxial graphene on step bunching of a 6H-SiC(0001) substrate: Aromatic ring pattern and Van Hove singularities

Laterally Inhomogeneous Au Intercalation in Epitaxial Graphene on SiC(0 0 0 1): A Multimethod Electron Microscopy Study

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