Cobalt Intercalation of Graphene on Silicon Carbide

Grebenyuk, G. S.; Lobanova, E. Yu.; Смирнов, Д. А.; Eliseyev, I. A.; Zubov, A. V.; Смирнов, А. Н.; Лебедев, С. П.; Davydov, V. Yu.; Lebedev, Alexander A.; Pronin, I. I.

doi:10.1134/s1063783419070102

Cited by 13 publications

(13 citation statements)

References 41 publications

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“…In fact, many previous reports on the intercalation of alkalis, − transition metals, ,, rare earths, ,, and other elements ,− have reported intercalation underneath the buffer layer (see ref for a brief review of intercalation of graphene on SiC). Furthermore, many prior studies on the intercalation of graphene on SiC have specifically reported the formation of silicide-like compounds, ,,, and thus, it is not surprising that we observe a surface Si component matching closely in binding energy with that of a Ca-silicide.…”

Section: Resultsmentioning

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%

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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: Resultsmentioning

confidence: 99%

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 formation of a metal silicide at the surface of the SiC after intercalation has been shown to occur with many other elements). [ 55,58–65 ] Importantly, it was found that Mg‐QFSBLG was relatively stable in ambient conditions for 6 h. [ 24 ] Additional measurements showed that Mg was unable to intercalate hydrogen‐intercalated quasi‐freestanding bilayer graphene on 6H‐SiC(0001) [ 24 ] —opening up the attractive possibility of a hybrid Mg/H intercalation procedure to create localized n‐p type junctions. To achieve intercalation, Mg was evaporated onto the graphene, and then the sample was annealed.…”

Section: Introductionmentioning

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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“…К настоящему моменту экспериментально изучен процесс интеркалирования графена, выращенного на карбиде кремния, переходными металлами Fe [7] и Co [8], и показано, что в зависимости от условий синтеза возможно формирование металлических пленок под графеном или твердого раствора металла в подложке. Также изучен процесс синтеза ферромагнитных силицидов под графеном путем его последовательного интеркалирования атомами кремния и металлов [9,10].…”

Section: Introductionunclassified

Электронная Структура Графена На Карбиде Кремния, Интеркалированного Атомами Кремния И Кобальта

Дунаевский¹,

Лобанова²,

Михайленко³

et al. 2021

Физика Твердого Тела

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The results of ab initio calculations of the spin-polarized band structure of graphene on silicon carbide intercalated with cobalt and silicon atoms are presented. It is shown that metal and silicon atoms during intercalation are localized between the substrate and the buffer layer of carbon atoms. Initially, the cobalt layer is strongly coupled with the buffer layer. The subsequent intercalation of silicon and the formation of cobalt silicide leads to a transition from hybridized state to the formation of quasi-freestanding bilayer graphene on the surface of the system due to the transformation of the buffer layer to the second graphene layer.

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Cobalt Intercalation of Graphene on Silicon Carbide

Cited by 13 publications

References 41 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)

Электронная Структура Графена На Карбиде Кремния, Интеркалированного Атомами Кремния И Кобальта

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