Rich essential properties of Si-doped graphene

Abstract

The diverse structural and electronic properties of the Si-adsorbed and-substituted monolayer graphene systems are studied by a complete theoretical framework under the first-principles calculations, including the adatom-diversified geometric structures, the Si-and C-dominated energy bands, the spatial charge densities, variations in the spatial charge densities and the atom-and orbital-projected density of states (DOSs). These critical physical quantities are unified together to display a distinct physical and chemical picture in the studying systems. Under the Si-adsorption and Si-substitution effects, the planar geometric structures are still remained mainly owing to the very strong CC and Si-C bonds on the honeycomb lattices, respectively. The Si-adsorption cases can create free carriers, while the finite-or zero-gap semiconducting behaviors are revealed in various Si-substitution configurations. The developed theoretical framework can be fully generalized to other emergent layered materials. The Si-doped graphene systems might be a highly promising anode material in the lithium-ion battery owing to its rich potential properties. Carbon atoms can form three-dimensional (3D) diamond 1 , 3D graphites 2 , two-dimensional (2D) graphene with the pure sp 2 carbon atoms 3 , 2D graphdiyne with the unique sp-sp 2 carbon atoms 4 , one-dimensional (1D) graphene nanoribbons 5-7 , 1D carbon nanotubes 8-10 , zero-dimensional (0D) carbon toroids 11,12 , 0D C 60-related fullerenes 13 , and 0D carbon onions 14. The versatile morphologies directly indicate the peculiar chemical bondings, in which all carbon-created systems possess sp 2-bonding surfaces except for the sp 3 bondings in diamond. Specifically, the few-and multi-layer graphene systems have been manufactured using the various methods 15,16 since the first experimental observation in 2004 by mechanical exfoliation. Up to now, they clearly exhibit plenty of remarkable fundamental properties due to the hexagonal symmetry, the nanoscaled thickness, and the distinct stacking configurations, such as semiconducting and semi-metallic behaviors 17,18 , anomalous quantum Hall effects 19 , diverse magnetic quantizations 20-23 , rich Coulomb excitations and decays 24-28 , different magnetooptical selection rules 29-31 , the exceedingly high mobility of charge carriers 32,33 , and the largest Young's modulus of materials ever tested 34. To induce the novel phenomena and extend the potential applications, the electronic properties can be easily modulated by the layer number 35,36 , stacking configuration 37-39 , mechanical strain 40,41 , sliding 42 , electric and magnetic field 43,44 , atom adsorption 45-48 and substitution 49-51. This paper mainly focuses on the latter two factors. How to modulate the fundamental properties becomes one of the mainstream topics in materials science, chemistry, physics and engineering. The chemical modification is the most effective method. Pristine graphene has a rather strong σ bonding of 2s, 2p x , and 2p y orbitals in a honeycomb lattice. This...

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