A DFT Study of B, N and BN Doped Graphene
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A DFT Study of B, N and BN Doped Graphene Pooja Rani and V. K. Jindal Department of Physics, Panjab University, Chandigarh-160014, India.
ABSTRACT We have made a density functional study of the structural and electronic properties of B or N (individual) doped and BN co-doped graphene. The effect of doping has been studied by incorporating the doping concentration amount varying from 2% (one atom of the dopant in 50 host atoms) to 12 % atomic concentration in case of individual doping and from 4% (2 atoms of the dopant in 50 host atoms) to 24 % in case of co-doping, at the same time, altering different doping sites for the same concentration of substitutional doping. We made use of VASP (Vienna Ab-Initio Simulation Package) software based on density functional theory to perform all calculations. While the resulting geometries do not show much of distortion on doping, the electronic properties show a transition from semimetal to semiconductor with increasing number of dopants. The study shows that the BN doping introduces the band gap at the Fermi level unlike individual B and N doping which causes the shifting of Fermi level above or below the Dirac point. It is observed that not only concentration but position of B and N atoms in the hetero-structure also affects the value of band gap introduced. INTRODUCTION Graphene, a single layer of sp2 hybridized carbon atoms arranged in a hexagonal lattice, has raised extensive interest in scientific world ever since its discovery in 2004 [1] for its unique electronic [2], mechanical [3] and optical properties [4]. Especially, the unique electronic properties, for example, outstanding ballistic transport properties and longest mean free path at room temperature [5], quantum hall effect [6] the highest mobility (of the order of 15000 cm2 V1 s-1 ) [7], finite conductivity even at zero charge carrier concentration, and so on have led to intense investigations in this field. Consequently, graphene has been considered as a preferred candidate for applications in future electronics. A pristine graphene layer is however a zero gap semiconductor (or semimetal) with a point like Fermi surface. Therefore, most electronic applications are limited by the absence of a semiconducting gap in pure graphene. For example, the transistors made from the zero-bandgap graphene (GFETs) have been able to achieve very small on-off ratios [1]. The development of graphene based electronics therefore depends on our ability to open a sizeable and well-tuned bandgap in graphene. Different approaches have been developed to fabricate high-performance graphene devices by engineering their band gaps so as to improve their semiconducting properties. In fact studies by different means like doping with heteroatoms [8], chemical functionalization [9] applying electric fields and depositing graphene on substrates like SiC, SiO 2 [10] have shown this possibility. It has been reported that the dopant atoms can modify the electronic band structure of graphene, and open up an energy gap between the valence and conduct
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