Bifunctional effects of the ordered Si atoms intercalated between quasi-free-standing epitaxial graphene and SiC(0001): graphene doping and substrate band bending

Kim, Hidong; Dugerjav, Otgonbayar; Arvisbaatar, Amarmunkh; Seo, Jae M.

doi:10.1088/1367-2630/17/8/083058

Cited by 10 publications

(16 citation statements)

References 71 publications

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“…[ 24 ] Relating the change in the intensity of the SiC peak (i.e., B C to B C ″ ) in the C 1s spectrum, to the magnitude of intercalation is not a new analysis technique, and various examples can be found in literature. [ 31,42,75,76 ] Thus, we expect that as the sample becomes more intercalated, component B C should diminish in photoemission intensity, and at the same time, component B C ″ (located at lower binding energy) should increase in photoemission intensity relative to the graphene peak at 284.83 ± 0.05 eV (labeled as “G” in Figure 4a,b, see the Supporting Information for further details on the graphene fitting procedure). That is, B c and B C ″ should possess an inverse relationship of the form:

\begin{matrix} {[{normalB}_{normalC}]}_{n} + {[{boldnormalB}_{C}'']}_{n} = {normalB}_{0} \end{matrix}

…”

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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\begin{matrix} {[{normalB}_{normalC}]}_{n} + {[{boldnormalB}_{C}'']}_{n} = {normalB}_{0} \end{matrix}

…”

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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“…Pristine EMLG shows two major components: BSi (EB = 101.47 ± 0.05 eV) corresponds to "bulk" SiC, 7,[32][33] and ZSi (EB = 101.83 ± 0.05 eV) to surface Si bonded to the C in the buffer layer/zero layer. 7,29,34 (The components corresponding to compounds present in both the Si 2p and C 1s XPS spectra are designated using the same label, with different subscript labels, in order to distinguish the specific core level, i.e., BSi and BC are the bulk SiC signals in the Si 2p and C 1s spectra, respectively). The corresponding atomic positions are shown schematically in the insets in Figs.…”

Section: X-ray Photoelectron Spectroscopy Of Ca-qfsblgmentioning

confidence: 99%

“…[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%

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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“…Intercalation of many species such as H, O, F, Au, Li, Na, Ge, Si and Yb [13][14][15][16][17][18][19][20][21][22] varied graphene doping in a wide range from n-doped to p-doped materials. Si and Ge, both from group IV, can be intercalated and effectively decouple the buffer layer from its supporting SiC substrate [19,20,23,24]. Si atoms can form two ordered structures at the interface depending on the annealing temperature, and the more ordered one obtained at higher temperature passivates the substrate more effectively with less electron doping [23].…”

Section: Introductionmentioning

confidence: 99%

“…Si and Ge, both from group IV, can be intercalated and effectively decouple the buffer layer from its supporting SiC substrate [19,20,23,24]. Si atoms can form two ordered structures at the interface depending on the annealing temperature, and the more ordered one obtained at higher temperature passivates the substrate more effectively with less electron doping [23]. Ge, similar to Au [16], produces ambipolar doping depending on the amount of intercalated atoms [19,24].…”

Section: Introductionmentioning

confidence: 99%

Metal-dielectric transition in Sn-intercalated graphene on SiC(0001)

2017

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The Sn intercalation into a buffer layer graphene grown on 4H-SiC(0001) substrate has been studied with spectroscopic photoemission and low energy electron microscope. Both SnSi x and SnOx interfacial layers are found to form below the buffer layer, converting it into a quasi-freestanding monolayer graphene. Combining the various operation modes of the microscope allows a detailed insight into the formation processes of the interlayers and their thermal stability. In particular, at the interface we observed a reversible transition from silicide to oxide after exposure to ambient pressure and subsequent annealing. This metal-dielectric transition might be useful for interface engineering in graphene-based devices.

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Bifunctional effects of the ordered Si atoms intercalated between quasi-free-standing epitaxial graphene and SiC(0001): graphene doping and substrate band bending

Cited by 10 publications

References 71 publications

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

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

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

Metal-dielectric transition in Sn-intercalated graphene on SiC(0001)

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