Atomistic Study of the Morphology of Graphene on Si and SiC Substrates
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Atomistic Study of the Morphology of Graphene on Si and SiC Substrates S. Seto, N. Arai, and K. Shintani Department of Mechanical Engineering and Intelligent Systems, University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585, Japan ABSTRACT The morphology of graphene on Si and SiC substrates is investigated using moleculardynamics simulation. The effects of the size and orientation of graphene on its roughness, distance from the substrate, and periodic structure are examined. The roughness and distance show the size dependency which agrees with the size dependency of the ratio of the periphery length of graphene to its area. It is found there are some cases in which the roughness of graphene can be suppressed. INTRODUCTION Graphene is expected to be a post-silicon material because of its superior electronic properties and adaptability for conventional thin-film technology. On selecting a substrate on which graphene is deposited, we must consider the stability of the structural and electronic properties of the deposited graphene, the feasibility for large-area growth, and the wide ranges of allowable temperature and pressure. It is well known both the electronic properties and morphology of graphene on a substrate depend on the kind of the elements constructing the substrate and the crystallographic orientation. Since its electronic properties also depend on the morphology of itself, adjusting the kind of the elements of substrates and the crystallographic orientation will lead to controlling the electronic properties of graphene. Candidate materials for such substrates are SiC [1, 2] and Si. 6H-SiC of (0001) surface and 4H-SiC of (11-20) surface are fabricated in industry. Heating 6H-SiC of (0001) surface leads to sublimation of Si atoms within upper layers and formation of large-area graphene consisting of C atoms left there; however, this method has a flaw that the layer number of the graphene resulting from such a process locally fluctuates. In recent years, 3C-SiC has been epitaxially grown on a Si substrate [3, 4]. Heating 3C-SiC on a Si substrate leads to formation of graphene on a Si substrate. By using this method of fabrication, graphene can be formed on Si substrates having (100), (110), and (111) surfaces. It was confirmed experimentally the band structure of such graphene changes depending on the crystallographic orientation of the substrate surface. However, for a Si substrate of (111) surface, the structure of SiC locally remained between graphene and the Si substrate, and the resulting band structure of graphene is different from that of graphene on Si. The surface roughness of graphene also affects the electronic properties of graphene. It is desirable that graphene is as flat as possible. In this research, the morphology of graphene on 6H-Si(0001), 4H-SiC(11-2), 3C-SiC(001), Si(100), Si(110), and Si(111) substrates is investigated by means of molecular-dynamics simulation. The effects of the size of graphene, the crystallographic orientation of substrates, and the relative arrang
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