On the effect of grain boundaries on the electronic and transport properties of graphene
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On the effect of grain boundaries on the electronic and transport properties of graphene Watheq Elias1,2, M. Elliott1 and C. C. Matthai1 1 School of Physics and Astronomy Cardiff University, The Parade, Cardiff, CF24 3AA, UK. 2 Department of Physics, College of Science, Koya University, Erbil, Iraq. E-mail: [email protected] ABSTRACT In studying large scale graphene structures it is necessary to consider the grain boundaries between the many single-crystal domains. The disruption of the crystallographic structure has consequences for both the electronic and transport properties. Although there has been much interest in this area in recent years, the size of system makes it difficult for ab initio methods to be applied to large structures and tight-binding models have provided some interesting results [1]. The semi-empirical Extended Hückel Theory (EHT) has advantage of being able to take account of charge reordering and to study very large systems. We have already applied this approach to study electrical transport across organic molecules and carbon nanoribbons. In this paper, we report on the results of EHT self-consistent calculations carried out to investigate the effect of grain boundaries on both the electronic structure and the electrical transport. INTRODUCTION Graphene is a two dimensional material consisting of a single layer of carbon atoms which has been synthesised experimentally in 2004 [2]. Since then graphene has attracted great interest in both the academic and commercial fields due to its extraordinary mechanical and electronic properties [3]. It is predicted, therefore, that the graphene could provide the basis for a wide range of technological devices and perhaps even replace the silicon in future electronics [3,4]. However, to fulfill these promises graphene needs to be produced on an industrial scale and most importantly of large-area sheets of single crystal. The most commonly employed method to fabricate large-scale graphene is chemical vapor deposition (CVD) [5]. In this technique, a metal foil, often copper, is used as the substrate on which the graphene is deposited. The size of graphene sheet produced is therefore restricted only by the size of the metal foil used. The graphene samples grown by CVD is polycrystalline where multi-single crystals are stitched together to form the entire sheet. Each of these single crystals is called a domain or grain and the interface between the two adjacent grains is termed a grain boundary (GB). The GBs and other topological defects in graphene could affect its properties and may have benefits or drawbacks on employing graphene in technological applications [6]. This leads us to the two long term aims in graphene research community: developing a reliable technique to produce large-scale graphene with control on the type and number of defects. Achieving these aims opens up endless possibilities for graphene applications. THE GBs STRUCTURE The atomic structure of a GB in polycrystalline graphene can be described by two translational vectors ⃗ and ⃗ of
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