A Nonzero Gap Two-dimensional Carbon Allotrope from Porous Graphene
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A Nonzero Gap Two-dimensional Carbon Allotrope from Porous Graphene Gustavo Brunetto1, Bruno I. Santos1, Pedro A. S. Autreto1, Leonadro D. Machado1, Ricardo P. B. dos Santos2, and Douglas S. Galvao1 1 Instituto de Física “Gleb Wataghin”, Universidade Estadual de Campinas, Campinas, SP 13083970, Brazil. 2 Departamento de Física, IGCE, UNESP, Rio Claro, SP, 13506-900, Brazil. ABSTRACT Graphene has been one of the hottest topics in materials science in the last years. Because of its special electronic properties graphene is considered one of the most promising materials for future electronics. However, in its pristine form graphene is a gapless semiconductor, which poses some limitations to its use in some transistor electronics. Many approaches have been tried to create, in a controlled way, a gap in graphene. These approaches have obtained limited successes. Recently, hydrogenated graphene-like structures, the so-called porous graphene, have been synthesized. In this work we show, based on ab initio quantum molecular dynamics calculations, that porous graphene dehydrogenation can lead to a spontaneous formation of a nonzero gap two-dimensional carbon allotrope, called biphenylene carbon (BC). Besides exhibiting an intrinsic nonzero gap value, BC also presents well delocalized frontier orbitals, suggestive of a structure with high electronic mobility. Possible synthetic routes to obtain BC from porous graphene are addressed. INTRODUCTION In the last few decades, many classes of new materials have been discovered. Among these new structures carbon-based materials attracted much attention due to new and useful properties. Examples of these materials are "colossal" carbon nanotubes [1] and graphene [2]. Graphene is a two-dimensional array of hexagonal units of sp2 bonded carbon atoms. It presents unusual and interesting electronic and mechanical properties [3]. Because of its special electronic properties, graphene is considered one of the most promising materials for future electronics [4]. However, in its pristine state graphene is a gapless semiconductor which limits its use in some classes of transistor electronics [5]. Many approaches have been tried in order to obtain a route to open, in a controlled way, a gap in graphene. The most common strategies exploits physical and/or chemical methods, such as, oxidation [6-11], hydrogenation [12-14] and/or fluorination [15]. These techniques have obtained limited successes because the electronic mobility, which is another important property that must be considered in the design of new electronic devices, can be partially compromised in these chemically modified graphenes. Another different approach is trying to obtain intrinsic nonzero gap graphene-like structures through direct synthesis. An example of this is the synthesis of hydrogenated structures, the so-called porous graphenes [16-19] (figure 1-(a)). An allotropic carbon phase that could combine intrinsic nonzero gap and high electronic mobility [20,21] would be an ideal structure to many electronics applications. A t
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