Doping modulation of quasi-free-standing monolayer graphene formed on SiC(0001) through Sn1-Ge  intercalation

Kim, Hidong; Dugerjav, Otgonbayar; Lkhagvasuren, Altaibaatar; Seo, Jae M.

doi:10.1016/j.carbon.2018.12.084

Cited by 17 publications

(15 citation statements)

References 25 publications

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“…The shift of SiC components towards lower binding energy due to band bending at the SiC surface has been observed in many other graphene on SiC intercalation experiments. 7,31,34,[43][44][48][49][50] The relative shifts in binding energy between components BSi/BC, ZSi/ZC, B Si '' /B C '' and Z Si '' /Z C '' can be found in Supporting Information Section 2.2, and further supports our assignment of these components.…”

Section: B Sisupporting

confidence: 78%

“…[35][36] This is strong evidence for a Ca-Si bonding environment at the SiC surface underneath the graphene and buffer layer and is in contrast with previous reports that Ca intercalates between the graphene layers, 12,19 or between the buffer layer and the 1 st graphene layer. 8,20 In fact, many reports have been made on the intercalation of alkalis, [37][38][39] transition metals, 31,[40][41] rare earths [9][10]42 and others elements 34,[43][44][45] underneath the buffer layer (see ref. 46 for a brief review of intercalation of graphene on SiC).…”

Section: X-ray Photoelectron Spectroscopy Of Ca-qfsblgmentioning

confidence: 99%

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Freestanding n-Doped Graphene via Intercalation of Calcium and Magnesium into the Buffer Layer–SiC(0001) Interface

Kotsakidis¹,

Čabo²,

Yin³

et al. 2020

Chem. Mater.

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The intercalation of epitaxial graphene on SiC(0001) with Ca has been studied extensively, yet precisely where the Ca resides remains elusive. Furthermore, the intercalation of Mg underneath epitaxial graphene on SiC(0001) has not been reported. Here, we use low energy electron diffraction, X-ray photoelectron spectroscopy, secondary electron cut-off photoemission and scanning tunneling microscopy to elucidate the structure of both Ca-and Mg-intercalated epitaxial graphene on SiC(0001). We find that in contrast to previous studies, Ca intercalates underneath the buffer layer and bonds to the Si-terminated SiC surface, breaking the C-Si bonds and 'freestanding' the buffer layer to form Ca-intercalated quasi-freestanding bilayer graphene (Ca-QFSBLG). This situation is similar with the Mg-intercalation of epitaxial graphene on SiC(0001), in which an ordered Mg-terminated reconstruction at the SiC surface is formed, resulting in Mgintercalated quasi-freestanding bilayer graphene (Mg-QFSBLG). We find no evidence that either Ca or Mg intercalates between graphene layers. However, we do find that both Ca-QFSBLG and Mg-QFSBLG exhibit very low workfunctions of 3.68 and 3.78 eV, respectively, indicating high n-type doping. Upon exposure to ambient conditions, we find Ca-QFSBLG degrades rapidly, whereas Mg-QFSBLG remains remarkably stable.

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Section: B Sisupporting

confidence: 78%

Section: X-ray Photoelectron Spectroscopy Of Ca-qfsblgmentioning

confidence: 99%

Freestanding n-Doped Graphene via Intercalation of Calcium and Magnesium into the Buffer Layer–SiC(0001) Interface

Kotsakidis¹,

Čabo²,

Yin³

et al. 2020

Chem. Mater.

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“…More recently, Briggs et al [ 68 ] used an oxygen/helium plasma to generate carbon vacancy defects in EMLG samples to help facilitate intercalation of (separately) Ga, Sn, and In layers underneath the buffer layer (in a process dubbed “confinement heteroepitaxy”). Although the intercalation of H, Ga, Sn, and In underneath the buffer layer of EMLG has been demonstrated by others using non‐engineered EMLG samples, [ 17,32,63,75,92 ] the engineering of defects (i.e., multi‐atomic discontinuities in the graphene) can significantly promote intercalation. [ 31,68,91 ]…”

Section: Resultsmentioning

confidence: 99%

Increasing the Rate of Magnesium Intercalation Underneath Epitaxial Graphene on 6H‐SiC(0001)

Kotsakidis

Currie

Čabo

et al. 2021

Adv Materials Inter

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in condensed matter physics experiments due to its ease of production (typically via micromechanical cleavage) [1,2] and access to novel physics owing to its linear "Dirac" band structure at low energy. [3,4] But for graphene to be useful in device applications, we must be able to engineer [5] its electrical properties. To achieve this, various techniques such as surface chemical doping [6] or atom substitution (see refs. [5,7] for a brief review of these methods), gating, [8][9][10][11][12][13] proximity effects, [8,14] stacking, [15,16] and intercalation [17][18][19][20][21][22][23][24][25] (see ref. [26] for a brief review of intercalation) have been applied. Of these techniques, intercalation (i.e., the insertion of atoms or molecules beneath or in-between graphene sheets) has been demonstrated as a relatively simple and versatile method for achieving control over graphene's key electrical properties-carrier type, [17][18][19]21] conductivity, [20,[27][28][29] and bandgap. [25,30] For instance, engineering the carrier type and bandgap via intercalation could enable graphene p-n junctions [31][32] and transistors. [33] Whereas increasing graphene's conductivity via intercalation could enable highly conductive and transparent electrodes for solar cells, [34] interconnects, [35] or new superconductors. [20,36] Many of the intercalation experiments to date have utilized epitaxially synthesized graphene on SiC (either the 4H-or 6H-polytype on the (0001) orientation, i.e., silicon Magnesium intercalated "quasi-freestanding" bilayer graphene on 6H-SiC(0001) (Mg-QFSBLG) has many favorable properties (e.g., highly n-type doped, relatively stable in ambient conditions). However, intercalation of Mg underneath monolayer graphene is challenging, requiring multiple intercalation steps. Here, these challenges are overcome and the rate of Mg intercalation is significantly increased by laser patterning (ablating) the graphene to form micron-sized discontinuities. Low energy electron diffraction is then used to verify Mg-intercalation and conversion to Mg-QFSBLG, and X-ray photoelectron spectroscopy to determine the Mg intercalation rate for patterned and non-patterned samples. By modeling Mg intercalation with the Verhulst equation, it is found that the intercalation rate increase for the patterned sample is 4.5 ± 1.7. Since the edge length of the patterned sample is ≈5.2 times that of the non-patterned sample, the model implies that the increased intercalation rate is proportional to the increase in edge length. Moreover, Mg intercalation likely begins at graphene discontinuities in pristine samples (not step edges or flat terraces), where the 2D-like crystal growth of Mg-silicide proceeds. The laser patterning technique may enable the rapid intercalation of other atomic or molecular species, thereby expanding upon the library of intercalants used to modify the characteristics of graphene, or other 2D materials and heterostructures.

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“…The optical and electronic properties directly correlate with alloy composition, wherein the dielectric function, band structure, superconductivity, and charge transfer from the metal to graphene are all controlled by the indium/gallium ratio in the 2D metal layer. toward this end, such as surface alloy phases on bulk metals [15][16][17][18][19][20][21][22][23] and the intercalation of Sn 1−x Ge x [24] at the EG/SiC(0001) interface motivate exploration of how 2D metal alloy composition enables tuning of the interband contributions to dielectric properties, alloy-dependent Fermi surface geometry, and other aspects of optical and electronic response. Here, we report the controlled synthesis and characterization of 2D-In x Ga 1−x alloys via CHet, using high-purity In and Ga metal precursors.…”

Section: Introductionmentioning

confidence: 99%

Tunable 2D Group‐III Metal Alloys

Rajabpour

Vera

et al. 2021

Advanced Materials

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Chemically stable quantum-confined 2D metals are of interest in next-generation nanoscale quantum devices. Bottom-up design and synthesis of such metals could enable the creation of materials with tailored, on-demand, electronic and optical properties for applications that utilize tunable plasmonic coupling, optical non-linearity, epsilon-near-zero behavior, or wavelengthspecific light trapping. In this work, we demonstrate that the electronic, superconducting and optical properties of air-stable two-dimensional metals can be controllably tuned by the formation of alloys. Environmentally robust large-area two-dimensional InxGa1-x alloys are synthesized by Confinement Heteroepitaxy (CHet). Near-complete solid solubility is achieved with no evidence of phase segregation, and the composition is tunable over the full range of x by changing the relative elemental composition of the precursor. The optical and electronic properties directly correlate with alloy composition, wherein the dielectric function, band structure, superconductivity, and charge transfer from the metal to graphene are all controlled by the indium/gallium ratio in the 2D metal layer.

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Doping modulation of quasi-free-standing monolayer graphene formed on SiC(0001) through Sn1-Ge intercalation

Cited by 17 publications

References 25 publications

Freestanding n-Doped Graphene via Intercalation of Calcium and Magnesium into the Buffer Layer–SiC(0001) Interface

Freestanding n-Doped Graphene via Intercalation of Calcium and Magnesium into the Buffer Layer–SiC(0001) Interface

Increasing the Rate of Magnesium Intercalation Underneath Epitaxial Graphene on 6H‐SiC(0001)

Tunable 2D Group‐III Metal Alloys

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