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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 total and partial density of states of 2 F-adsorbed graphene case C with band-gap opening of 0.37 eV. Similar figures for the other cases are included in the Supporting Information.
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fig10: The total and partial density of states of 2 F-adsorbed graphene case C with band-gap opening of 0.37 eV. Similar figures for the other cases are included in the Supporting Information.

Mentions: The calculated energy gaps and band widths of BF for 2 F-adsorbed graphene with the ten binding configurations are listed in Table 3. The calculated charges on fluorine and CF atoms are also listed in Table 3. Obviously, after bonding with CF, fluorine obtains electrons from CF and its near neighbor carbon atoms. Since CF has sp3 hybridization, and the nearest carbons possess sp3–sp2 crossover to fully sp2-hybridized carbons, such structural change causes important distortion of the lattice (buckling the graphene).13d Both of these carbons donate electrons to fluorine atoms. Figure 9 shows the TDOS of all 2 F-adsorbed graphene configurations around the EF region. The complete TDOS of these 2 F-adsorbed graphene configurations are shown in Figure S1 in the Supporting Information. As an example, Figure 10 shows the PDOS of the two binding configurations in case C. By closely examining the TDOS around the Fermi level in Figure 9, the PDOS of 7×7×1 pure graphene, and the PDOS of eight other binding configurations (cases A, B, D, and E) shown in Figures S2–S6 in the Supporting Information, one can see that after F-adsorption, the VB around the Fermi level is mainly due to contributions from fluorine 2p orbitals. Clearly, fluorine adsorption significantly alters the electronic structure of graphene in a manner that depends on the defect structures.


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 total and partial density of states of 2 F-adsorbed graphene case C with band-gap opening of 0.37 eV. Similar figures for the other cases are included in the Supporting Information.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig10: The total and partial density of states of 2 F-adsorbed graphene case C with band-gap opening of 0.37 eV. Similar figures for the other cases are included in the Supporting Information.
Mentions: The calculated energy gaps and band widths of BF for 2 F-adsorbed graphene with the ten binding configurations are listed in Table 3. The calculated charges on fluorine and CF atoms are also listed in Table 3. Obviously, after bonding with CF, fluorine obtains electrons from CF and its near neighbor carbon atoms. Since CF has sp3 hybridization, and the nearest carbons possess sp3–sp2 crossover to fully sp2-hybridized carbons, such structural change causes important distortion of the lattice (buckling the graphene).13d Both of these carbons donate electrons to fluorine atoms. Figure 9 shows the TDOS of all 2 F-adsorbed graphene configurations around the EF region. The complete TDOS of these 2 F-adsorbed graphene configurations are shown in Figure S1 in the Supporting Information. As an example, Figure 10 shows the PDOS of the two binding configurations in case C. By closely examining the TDOS around the Fermi level in Figure 9, the PDOS of 7×7×1 pure graphene, and the PDOS of eight other binding configurations (cases A, B, D, and E) shown in Figures S2–S6 in the Supporting Information, one can see that after F-adsorption, the VB around the Fermi level is mainly due to contributions from fluorine 2p orbitals. Clearly, fluorine adsorption significantly alters the electronic structure of graphene in a manner that depends on the defect structures.

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