Chemically Resolved Interface Structure of Epitaxial Graphene on SiC(0001)

Emery, Jonathan D.; Detlefs, Blanka; Karmel, Hunter J.; Nyakiti, Luke O.; Gaskill, D. Kurt; Hersam, Mark C.; Zegenhagen, J.; Bedzyk, Michael J.

doi:10.1103/physrevlett.111.215501

Cited by 79 publications

(87 citation statements)

References 34 publications

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“…It is more likely that the buffer graphene is bonded to the SiC through a smaller number of sites consistent with STM measurements that suggest the buffer lies above a small set of Si trimers [24]. A reduced buffer-SiC bonding geometry is also consistent with both x-ray scattering [25] and x-ray standing wave experiments [26], which find a reduced Si concentration and an increased C concentration in the SiC layer below the buffer. We suggest that the reduced substrate bonding would still be sufficient to strain the buffer and produce the ribbon network.…”

Section: Prl 115 136802 (2015) P H Y S I C a L R E V I E W L E T T Esupporting

confidence: 71%

Graphene Gets a Good Gap

Lanzara

2015

Physics

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While numerous methods have been proposed to produce semiconducting graphene, a significant band gap has never been demonstrated. The reason is that, regardless of the theoretical gap formation mechanism, subnanometer disorder prevents the required symmetry breaking necessary to make graphene semiconducting. In this work, we show for the first time that semiconducting graphene can be made by epitaxial growth. Using improved growth methods, we show by direct band measurements that a band gap greater than 0.5 eV can be produced in the first graphene layer grown on the SiC(0001) surface. This work demonstrates that order, a property that remains lacking in other graphene systems, is key to producing electronically viable semiconducting graphene. DOI: 10.1103/PhysRevLett.115.136802 PACS numbers: 73.22.Pr, 79.60.Bm, 79.60.Jv, 81.05.ue It is well known that the first graphene layer grown on the SiC(0001) surface is not electronic graphene. That is, the first "buffer" graphene layer does not show the linear dispersing π bands (Dirac cone) expected at the K point of metallic graphene [1][2][3]. The lack of π bands in experimental band maps of the buffer layer [2] supported the theoretical conclusion that sufficiently strong covalent bonds between the buffer layer and the SiC interface would push the graphene π bands below the SiC valence band maximum [4,5]. Aside from these very early studies, research on the SiC graphene buffer layer faded and was subsequently eclipsed by a wide variety of other unsuccessful ideas to open a band gap in exfoliated or chemical vapor deposition (CVD)-grown graphene [6].One method to open a band gap in graphene is by periodic bonding to either all A or all B sites, which breaks graphene's chiral symmetry (referred to as graphene functionalization). The buffer graphene, commensurately bonded to the SiC(0001) surface, should have been an excellent example of a functionalized system. Despite the buffer graphene's potential to be functionalized by a commensurate and, most importantly, ordered array of Si or C atoms at the SiC surface, there was instead a major research shift to functionalize CVD-grown graphene. As of this writing, no functionalized graphene, or graphene modified by any other proposed method, has been developed that produces a workable semiconducting form of graphene. The problem with these methods is the inherent disorder introduced by the functionalization [7,8] and growth processes [6]. In fact, the lack of a graphene band gap was the motivation to shift research to metal dichalcogenides despite the inability to grow them at the level of purity and order required for scalable electronics.In this work, we use furnace-grown graphene to produce a structurally well-ordered buffer graphene (BG) on the SiC(0001) surface. Angle-resolved photoemission (ARPES) measurements show new dispersing π bands that are not observed in samples grown by previous methods. These bands live above the SiC valence band maximum near the Fermi energy E F . The new band structure is a result of impr...

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Section: Prl 115 136802 (2015) P H Y S I C a L R E V I E W L E T T Esupporting

confidence: 71%

Graphene Gets a Good Gap

Lanzara

2015

Physics

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“…In both cases an interface structure is present; however, at the Si face this is composed only of C [11] and has a well-defined honeycomb geometry [10]. On the other hand, the C-terminated amorphous layer shows chemical signatures of three elements (C, Si, and O) and it is significantly thicker.…”

Section: Discussionmentioning

confidence: 99%

“…A starting point for understanding this critical issue is the morphology of the graphene/SiC interface. At the Si face, a well defined interface structure has been identified by means of both experimental [9][10][11][12] and theoretical studies [13,14], which is thought to influence both the epitaxial process as well as the electrical characteristics [15] of the overlying graphene. This so-called buffer layer has a (6 √ 3 × 6 √ 3)R30…”

Section: Introductionmentioning

confidence: 99%

Interface disorder probed at the atomic scale for graphene grown on the C face of SiC

et al. 2015

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Interface disorder probed at the atomic scale for graphene grown on the C face of SiC, 2015, Physical Review B. Condensed Matter and Materials Physics, (91) We use aberration-corrected scanning transmission electron microscopy, electron energy-loss spectroscopy, atomic force microscopy, and the density functional theory to study the structural and electronic characteristics of graphene grown on the C face of SiC. We show that for high growth temperatures the graphene/SiC (0001) interface is dominated by a thin amorphous film which strongly suppresses the epitaxy of graphene on the SiC substrate. This film maintains an almost fixed thickness regardless of the number of the overlying graphene layers, while its chemical signature shows the presence of C, Si, and O. Structurally, the amorphous area is inhomogeneous, as its Si concentration gradually decreases while approaching the first graphene layer, which is purely sp 2 hybridized. Ab initio calculations show that the evaporation process and the creation of Si vacancies on the C face of SiC strongly enhance the surface disorder and designate defect areas as preferential sublimation sites. Based on these features, we discuss differences and similarities between the C-only buffer layer that forms on the Si face of SiC and the thicker C-Si-O amorphous film of the C face.

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“…There exists evidence that up to 30% of the carbon atoms in the semiconductor-like transition carbon layer (called also the buffer layer, zero graphene layer or interfacial layer) are covalently bonded to the Si atoms (belonging to SiC) by sp 3 hybridized bonds [1][2][3]. It is believed that the first graphene layer fits into a (6 √ 3 × 6 √ 3) R30 • surface reconstruction on SiC, and the (6 √ 3 × 6 √ 3) R30 • unit cell ideally coincides with a graphene unit.…”

Section: Introductionmentioning

confidence: 99%

Role of the Potential Barrier in the Electrical Performance of the Graphene/SiC Interface

et al. 2017

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Abstract:In spite of the great expectations for epitaxial graphene (EG) on silicon carbide (SiC) to be used as a next-generation high-performance component in high-power nano-and micro-electronics, there are still many technological challenges and fundamental problems that hinder the full potential of EG/SiC structures and that must be overcome. Among the existing problems, the quality of the graphene/SiC interface is one of the most critical factors that determines the electroactive behavior of this heterostructure. This paper reviews the relevant studies on the carrier transport through the graphene/SiC, discusses qualitatively the possibility of controllable tuning the potential barrier height at the heterointerface and analyses how the buffer layer formation affects the electronic properties of the combined EG/SiC system. The correlation between the sp 2 /sp 3 hybridization ratio at the interface and the barrier height is discussed. We expect that the barrier height modulation will allow realizing a monolithic electronic platform comprising different graphene interfaces including ohmic contact, Schottky contact, gate dielectric, the electrically-active counterpart in p-n junctions and quantum wells.

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Chemically Resolved Interface Structure of Epitaxial Graphene on SiC(0001)

Cited by 79 publications

References 34 publications

Graphene Gets a Good Gap

Graphene Gets a Good Gap

Interface disorder probed at the atomic scale for graphene grown on the C face of SiC

Role of the Potential Barrier in the Electrical Performance of the Graphene/SiC Interface

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