Charge spill-out and work function of few-layer graphene on SiC(0 0 0 1)

Renault, O.; Pascon, Aline M.; Rotella, H.; Kaja, Khaled; Mathieu, Claire; Rault, Julien; Blaise, P.; Poiroux, T.; Barrett, N.; Fonseca, L. R. C.

doi:10.1088/0022-3727/47/29/295303

Cited by 15 publications

(15 citation statements)

References 45 publications

(64 reference statements)

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“…Hence, the measured height must be influenced by the electronic properties of the system in a way that the measurement grossly overestimates the true island height. Recently, the work function of MLG on SiC has been determined experimentally to be in the range of 4.05 − 4.28 eV, which is considerably lower than the 5.55 eV quoted for Co(0001) . Due to the larger work function of Co one would expect the STM to measure smaller island heights in contrast to the findings in our experiments.…”

Section: Resultscontrasting

confidence: 90%

Sub‐Monolayer Growth of Titanium, Cobalt, and Palladium on Epitaxial Graphene

et al. 2017

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We deposited metals (Ti, Co, Pd) typically used as seed layers for contacts on epitaxial graphene on SiC(0001) and studied the early stages of growth in the sub-monolayer regime by Scanning Tunneling Microscopy (STM). All three metals do not wet the substrate and Ostwalt ripening occurs at temperatures below 400 K. The analysis of the epitaxial orientation of the metal adislands revealed their specific alignment to the graphene lattice. It is found that the apparent height of the islands as measured by STM strongly deviates from their true topographic height. This is interpreted as an indication of the presence of scattering processes within the metal particles that increase the transparency of the metal-graphene interface for electrons. Even large islands are easily picked up by the tip of the STM allowing insight into the bonding between metal island and graphene surface and into mechanisms leading to metal intercalation.

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Section: Resultscontrasting

confidence: 90%

Sub‐Monolayer Growth of Titanium, Cobalt, and Palladium on Epitaxial Graphene

et al. 2017

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“…16 equal and close to that of freestanding graphene at the same strain (4.9 eV). This is in contrast to that found for graphene grown on the clean SiC(0001) surface [45], where the work function increases by 135meV when moving from the 1LG to the 2LG surface, which can be attributed to an electrostatic origin [46].…”

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confidence: 83%

Charge neutrality in epitaxial graphene on6H-SiC(0001) via nitrogen intercalation

et al. 2015

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The electronic properties of epitaxial graphene grown on SiC(0001) are known to be impaired relative to those of freestanding graphene. This is due to the formation of a carbon buffer layer between the graphene layers and the substrate, which causes the graphene layers to become strongly n-doped. Charge neutrality can be achieved by completely passivating the dangling bonds of the clean SiC surface using atomic intercalation. So far, only one element, hydrogen, has been identified as a promising candidate. We show, using first-principles density functional calculations, how it can also be accomplished via the growth of a thin layer of silicon nitride on the SiC surface. The subsequently grown graphene layers display the electronic properties associated with charge neutral graphene. We show that the surface energy of this structure is considerably lower than that of others with intercalated atomic nitrogen and determine how its stability depends on the N 2 chemical potential. The thermal decomposition of silicon carbide (SiC) is one of the most promising methods to produce high-quality epitaxial graphene on a wafer scale, directly on a semiconducting surface. However, the electronic properties of the resultant graphene have been shown to depend intimately on the chosen SiC surface. When graphene is grown on the Si-rich SiC(0001) surface, the first carbon layer is covalently bonded to the surface Si atoms, with only subsequent layers displaying the characteristic electronic features of graphene. Furthermore, these graphene layers are heavily doped, due to charge transfer from the surface, and have a considerably reduced electron mobility compared to freestanding graphene [1][2][3].Several attempts have been made to electronically decouple the so-called carbon buffer layer or "zeroth layer" graphene (0LG) from the substrate and thereby reduce the intrinsic electron doping. A promising technique to do so is by intercalating atoms or molecules between the 0LG and the SiC substrate [4][5][6][7][8]. Hydrogen intercalation has been shown to reproducibly decouple the buffer layer from the substrate [9], increasing the carrier mobility to more than 11000 cm 2 V −1 s −1 at 0.3 K [10]. However, the resulting quasifreestanding monolayer graphene is slightly p-doped [11] due to the intrinsic spontaneous polarization of hexagonal SiC [12,13].Attaining charge neutrality is vital to achieve the high electron mobilities associated with freestanding or suspended graphene [14]. The intercalation of highly electronegative atoms, such as N, O, and F, could be expected to reduce or even eliminate the intrinsic n-type doping of graphene. However, F intercalation results in strong p-doping [15], while O intercalation is difficult to control [16][17][18]. The effect of nitrogen intercalation on the electronic structure of graphene on SiC has only recently been addressed. Wang et al. [19] showed that, after thermal treating with NH 3 , dissociated N species intercalate between the 0LG and the substrate, weakening the interaction between t...

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“…In this regard, important research effort has been performed to study the relationship between graphene thickness and WF. The WF of graphene with more than one layer is known to be dependent on the number of layers due to the charge transfer at the substrate interface and the charge distribution within the different layers of graphene [50]. The results of PEEM studies revealed that, by increasing the number of graphene layers, the C1s core level shifted to lower binding energies as a result of the thickness dependence of the Dirac point energy ( Figure 3a) [44].…”

Section: Thickness Dependence Of the Graphene Work Functionmentioning

confidence: 99%

Tuning the work function of graphene toward application as anode and cathode

Naghdi

Sánchez‐Arriaga

Rhee

2019

Journal of Alloys and Compounds

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The rapid technological progress in the 21 st century demands new multi-functional materials applicable to a wide variety of industries. Two-dimensional (2D) materials are predicted to have a revolutionary impact on the cost, size, weight, and functions of future electronic and optoelectronic devices. Graphene, which shows potential as an alternative to conventional conductive transparent metal oxides, may play a central role. Since its work function (WF) is tunable, graphene exhibits the interesting ability to serve two different roles in electronic and optoelectronic devices, both as an anode and a cathode.After introducing some basic concepts, this work reviews the most important advances in controlling the tuned WF of graphene, highlighting special features of graphene electronic band structure and recognizing different methods for measuring WF. The impact of thickness, type of contact, chemical doping, UV and plasma treatments, defects, and functional groups of graphene oxide are considered and related with the applications of the modulated material. The results of the review, organized in lookup tables, have been used to identify the advantages and main challenges of the tuning methods.

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Charge spill-out and work function of few-layer graphene on SiC(0 0 0 1)

Cited by 15 publications

References 45 publications

Sub‐Monolayer Growth of Titanium, Cobalt, and Palladium on Epitaxial Graphene

Sub‐Monolayer Growth of Titanium, Cobalt, and Palladium on Epitaxial Graphene

Charge neutrality in epitaxial graphene on6H-SiC(0001) via nitrogen intercalation

Tuning the work function of graphene toward application as anode and cathode

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