Carrier type inversion in quasi-free standing graphene: studies of local electronic and structural properties

Melios, Christos; Panchal, Vishal; Giusca, Cristina E.; Strupiński, Włodek; Silva, S. Ravi P.; Kazakova, Olga

doi:10.1038/srep10505

Cited by 49 publications

(66 citation statements)

References 35 publications

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“…Recently, KPFM measurements have been successfully employed to identify the different step configurations and number of layers in epitaxial graphene on SiC(0001) substrate . More recently, it has been demonstrated that this method can also provide direct access for the identification of graphene domains with different type of doping . In Figure a,b, and c, we show the STM, non‐contact atomic force microscopy (NC‐AFM) topography and simultaneously measured KPFM images of a surface region covered in areas of single‐layer, bilayer, and Pb‐intercalated graphene on SiC substrate, respectively.…”

Section: Resultsmentioning

confidence: 99%

Effects of Pb Intercalation on the Structural and Electronic Properties of Epitaxial Graphene on SiC

Yurtsever

Onoda

Iimori

et al. 2016

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The effects of Pb intercalation on the structural and electronic properties of epitaxial single-layer graphene grown on SiC(0001) substrate are investigated using scanning tunneling microscopy (STM), noncontact atomic force microscopy, Kelvin probe force microscopy (KPFM), X-ray photoelectron spectroscopy, and angle-resolved photoemission spectroscopy (ARPES) methods. The STM results show the formation of an ordered moiré superstructure pattern induced by Pb atom intercalation underneath the graphene layer. ARPES measurements reveal the presence of two additional linearly dispersing π-bands, providing evidence for the decoupling of the buffer layer from the underlying SiC substrate. Upon Pb intercalation, the Si 2p core level spectra show a signature for the existence of PbSi chemical bonds at the interface region, as manifested in a shift of 1.2 eV of the bulk SiC component toward lower binding energies. The Pb intercalation gives rise to hole-doping of graphene and results in a shift of the Dirac point energy by about 0.1 eV above the Fermi level, as revealed by the ARPES measurements. The KPFM experiments have shown that decoupling of the graphene layer by Pb intercalation is accompanied by a work function increase. The observed increase in the work function is attributed to the suppression of the electron transfer from the SiC substrate to the graphene layer. The Pb intercalated structure is found to be stable in ambient conditions and at high temperatures up to 1250 °C. These results demonstrate that the construction of a graphene-capped Pb/SiC system offers a possibility of tuning the graphene electronic properties and exploring intriguing physical properties such as superconductivity and spintronics.

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Section: Resultsmentioning

confidence: 99%

Effects of Pb Intercalation on the Structural and Electronic Properties of Epitaxial Graphene on SiC

Yurtsever

Onoda

Iimori

et al. 2016

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“…We first employ KPFM in order to construct a layer-resolved image of the graphene structure. It has been shown, that KPFM is a powerful technique that enables mapping of the surface potential (SP) variations between different graphene layers, thus constructing a nanometer resolution map of the SP [28]. Here, FM-KPFM is used in a single pass mode, where the topography and the SP of the sample are measured simultaneously at different frequencies.…”

Section: Resultsmentioning

confidence: 99%

Surface and interface structure of quasi-free standing graphene on SiC

et al. 2016

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We perform local nanoscale studies of the surface and interface structure of hydrogen intercalated graphene on 4H-SiC(1000). In particular, we show that intercalation of the interfacial layer results in the formation of quasi-free standing one layer graphene (QFS 1LG) with change in the carrier type from n-to p-type, accompanied by a more than four times increase in carrier mobility. We demonstrate that surface enhanced Raman scattering (SERS) reveals the enhanced Raman signal of Si-H stretching mode, which is the direct proof of successful intercalation. Furthermore, the appearance of D, D +D' as well as C-H peaks for the quasi-free standing two layer graphene (QFS 2LG) suggests that hydrogen also penetrates in between the graphene layers to locally form C-H sp 3 defects that decrease the mobility. Thus, SERS provides a quick and reliable technique to investigate the interface structure of graphene which is in general not accessible

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“…The measured surface potential difference between terrace and edges is 40 ± 10 mV for both samples. This correlation between surface potential contrast (from KPFM measurement) and number of layers (from LEEM analysis) has been ascribed to different substrate induced doping levels, as a result of the different energy dispersions of mono-and bilayer graphene [20,32,33]. Additionally, for the case of SLG a possible origin of the different doping of graphene at the steps regions could be a different interface structure between graphene and the substrate, with a local delamination of the buffer layer on the steps [34,35].…”

Section: Peem Image Ofmentioning

confidence: 95%

Structural characterization of as-grown and quasi-free standing graphene layers on SiC

Bueno

Palacio

Munuera

et al. 2019

Applied Surface Science

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We report on a comparative structural characterization of two types of high quality epitaxial graphene layers grown by CVD on 4H-SiC(0001). The layers under study are a single layer graphene on top of a buffer layer and a quasi-free-standing graphene obtained by intercalation of hydrogen underneath the buffer layer. We determine the morphology and structure of both layers by different complementary in-situ and ex-situ surface techniques. We found the existence of large islands in both samples but with different size distribution. Photoemission electron microscopy (PEEM) measurements were performed to get information about the chemical environment of the different regions. The study reveals that monolayer graphene prevails in most of the surface terraces, while a bilayer and trilayer graphene presence is observed at the steps, stripes along steps and islands.

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Carrier type inversion in quasi-free standing graphene: studies of local electronic and structural properties

Cited by 49 publications

References 35 publications

Effects of Pb Intercalation on the Structural and Electronic Properties of Epitaxial Graphene on SiC

Effects of Pb Intercalation on the Structural and Electronic Properties of Epitaxial Graphene on SiC

Surface and interface structure of quasi-free standing graphene on SiC

Structural characterization of as-grown and quasi-free standing graphene layers on SiC

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