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Electronic Structures, Bonding Configurations, and Band-Gap-Opening Properties of Graphene Binding with Low-Concentration Fluorine.

Duan Y, Stinespring CD, Chorpening B - ChemistryOpen (2015)

Bottom Line: The lowest-binding energy state is found to correspond to two CF defects on nearest neighbor sites, with one fluorine above the carbon plane and the other below the plane.The binding energy decreases with decreasing fluorine concentration due to the interaction between neighboring fluorine atoms.The obtained results are useful for sensor development and nanoelectronics.

View Article: PubMed Central - PubMed

Affiliation: National Energy Technology Laboratory, United States Department of Energy 626 Cochrans Mill Road, Pittsburgh, PA, 15236, USA.

ABSTRACT
To better understand the effects of low-level fluorine in graphene-based sensors, first-principles density functional theory (DFT) with van der Waals dispersion interactions has been employed to investigate the structure and impact of fluorine defects on the electrical properties of single-layer graphene films. The results show that both graphite-2 H and graphene have zero band gaps. When fluorine bonds to a carbon atom, the carbon atom is pulled slightly above the graphene plane, creating what is referred to as a CF defect. The lowest-binding energy state is found to correspond to two CF defects on nearest neighbor sites, with one fluorine above the carbon plane and the other below the plane. Overall this has the effect of buckling the graphene. The results further show that the addition of fluorine to graphene leads to the formation of an energy band (BF) near the Fermi level, contributed mainly from the 2p orbitals of fluorine with a small contribution from the p orbitals of the carbon. Among the 11 binding configurations studied, our results show that only in two cases does the BF serve as a conduction band and open a band gap of 0.37 eV and 0.24 eV respectively. The binding energy decreases with decreasing fluorine concentration due to the interaction between neighboring fluorine atoms. The obtained results are useful for sensor development and nanoelectronics.

No MeSH data available.


Related in: MedlinePlus

The calculated band structure of a) graphite-2 H and b) graphene.
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fig06: The calculated band structure of a) graphite-2 H and b) graphene.

Mentions: Figure 6 a gives the band structure of graphite-2 H (space group P63/mmc (#196)).24 The total density of states (TDOS) and projected atomic partial density of states (PDOS) of graphite-2H are shown in Figure 7 a. Since the graphite unit cell contains four carbon atoms, there are eight occupied bands in its valence band (VB) It can be clearly seen that the graphite-2 H has zero band gap along the highly symmetrical H–K points, and its DOS is characterized by a very low value at the Fermi-level EF, which is in good agreement with other reported results.26 From the PDOS shown in Figure 7 a, it may be seen that the VB is composed of carbon s and p orbitals, with the s orbital dominating at lower energies, and the p orbitals being more pronounced at higher energies just below the Fermi-level EF.26a The reason is that the s orbital of carbon participates in building up the sp2 hybrids to form low-lying σ bands as shown in Figure 6 a, while the higher-lying π bands have pz character only. The low value of the DOS at EF is also well documented from XPS measurements27 and in other theoretical reports.26a,28


Electronic Structures, Bonding Configurations, and Band-Gap-Opening Properties of Graphene Binding with Low-Concentration Fluorine.

Duan Y, Stinespring CD, Chorpening B - ChemistryOpen (2015)

The calculated band structure of a) graphite-2 H and b) graphene.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4608533&req=5

fig06: The calculated band structure of a) graphite-2 H and b) graphene.
Mentions: Figure 6 a gives the band structure of graphite-2 H (space group P63/mmc (#196)).24 The total density of states (TDOS) and projected atomic partial density of states (PDOS) of graphite-2H are shown in Figure 7 a. Since the graphite unit cell contains four carbon atoms, there are eight occupied bands in its valence band (VB) It can be clearly seen that the graphite-2 H has zero band gap along the highly symmetrical H–K points, and its DOS is characterized by a very low value at the Fermi-level EF, which is in good agreement with other reported results.26 From the PDOS shown in Figure 7 a, it may be seen that the VB is composed of carbon s and p orbitals, with the s orbital dominating at lower energies, and the p orbitals being more pronounced at higher energies just below the Fermi-level EF.26a The reason is that the s orbital of carbon participates in building up the sp2 hybrids to form low-lying σ bands as shown in Figure 6 a, while the higher-lying π bands have pz character only. The low value of the DOS at EF is also well documented from XPS measurements27 and in other theoretical reports.26a,28

Bottom Line: The lowest-binding energy state is found to correspond to two CF defects on nearest neighbor sites, with one fluorine above the carbon plane and the other below the plane.The binding energy decreases with decreasing fluorine concentration due to the interaction between neighboring fluorine atoms.The obtained results are useful for sensor development and nanoelectronics.

View Article: PubMed Central - PubMed

Affiliation: National Energy Technology Laboratory, United States Department of Energy 626 Cochrans Mill Road, Pittsburgh, PA, 15236, USA.

ABSTRACT
To better understand the effects of low-level fluorine in graphene-based sensors, first-principles density functional theory (DFT) with van der Waals dispersion interactions has been employed to investigate the structure and impact of fluorine defects on the electrical properties of single-layer graphene films. The results show that both graphite-2 H and graphene have zero band gaps. When fluorine bonds to a carbon atom, the carbon atom is pulled slightly above the graphene plane, creating what is referred to as a CF defect. The lowest-binding energy state is found to correspond to two CF defects on nearest neighbor sites, with one fluorine above the carbon plane and the other below the plane. Overall this has the effect of buckling the graphene. The results further show that the addition of fluorine to graphene leads to the formation of an energy band (BF) near the Fermi level, contributed mainly from the 2p orbitals of fluorine with a small contribution from the p orbitals of the carbon. Among the 11 binding configurations studied, our results show that only in two cases does the BF serve as a conduction band and open a band gap of 0.37 eV and 0.24 eV respectively. The binding energy decreases with decreasing fluorine concentration due to the interaction between neighboring fluorine atoms. The obtained results are useful for sensor development and nanoelectronics.

No MeSH data available.


Related in: MedlinePlus