Properties of epitaxial graphene grown on C-face SiC compared to Si-face
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Epitaxial graphene of uniform thickness prepared on SiC is of great interest for various applications. On the Si-face, large area uniformity has been achieved, and there is a general consensus about the graphene properties. A similar uniformity has yet not been demonstrated on the C-face where the graphene has been claimed to be fundamentally different. A rotational disorder between adjacent graphene layers has been reported and suggested to explain why multilayer C-face graphene show the p-band characteristic of monolayer graphene. Utilizing low energy electron microscopy, x-ray photoelectron electron microscopy, low energy electron diffraction, and photoelectron spectroscopy, we investigated the properties of C-face graphene prepared by sublimation growth. We observe the formation of micrometer-sized crystallographic grains of multilayer graphene and no rotational disorder between adjacent layers within a grain. Adjacent grains are in general found to have different azimuthal orientations. Effects on C-face graphene by hydrogen treatment and Na exposure were also investigated and are reported. Why multilayer C-face graphene exhibits single layer electronic properties is still a puzzle, however.
I. INTRODUCTION
Graphene-based two-dimensional science and technology has developed into a new interdisciplinary area that has made a major impact on both fundamental and applied materials research. The current status of different graphene subfields and the wide range of graphene applications envisioned for the future are comprehensively described by the articles in the recent extended issue1 of MRS Bulletin, “Graphene, fundamentals and functionalities.” Graphene can be produced/grown using different methods,1 but in this article, only properties of graphene grown epitaxially on the basal plane of the wide band gap semiconductor silicon carbide are discussed. This growth method is considered a most promising route2–4 for the development of carbon nanoelectronics based on lithographic patterning of graphene. Large-scale epitaxial films with atomic layer-defined termination are highly desirable for electronic applications and also for fundamental studies of graphene functionalization. Methods to reliably grow high-quality graphene films with large-scale uniformity on SiC(0001), i.e., the Si-terminated surface, have been developed4–8 but for the C-terminated SiC(000–1) surface graphene films9–14 with similar large-scale uniformity has so far not been possible to produce.
Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] This paper has been selected as an Invited Feature Paper. DOI: 10.1557/jmr.2013.261 426
J. Mater. Res., Vol. 29, No. 3, Feb 14, 2014
http://journals.cambridge.org
Downloaded: 11 Mar 2015
Already in one of the earliest comparative studies15 of the growth of carbon layers on the basal plane of 6H-SiC, it was reported that large single crystalline graphite layers could be obtained on the Si-face while the layers on the C-face had a significant polycrystalline char
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