Doping of fluorographene by surface adsorbates

A. Markevich, R. Jones, and P. R. Briddon

Phys. Rev. B 84, 115439 – Published 22 September 2011

Abstract

Density functional theory is used to investigate the possibility of doping fluorographene by surface adsorbates. The structure and electronic properties of fluorographene with adsorbed K, Li, Au atoms, and F4-TCNQ molecule are described. It is shown that adsorption of K or Li atoms results in electron doping of fluorographene, while Au atoms and F4-TCNQ introduce deep levels inside the band gap. The calculated value of the fluorographene work function is extremely high, 7.3 eV, suggesting that p-type doping is difficult to achieve.

Received 11 July 2011

DOI:https://doi.org/10.1103/PhysRevB.84.115439

Authors & Affiliations

A. Markevich^1,*, R. Jones¹, and P. R. Briddon²

¹College of Engineering, Mathematics and Physical Sciences, University of Exeter, Stocker Road, Exeter, EX4 4QL, United Kingdom
²School of Electrical, Electronic and Computer Engineering, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom

^*avmark@excc.ex.ac.uk

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Issue

Vol. 84, Iss. 11 — 15 September 2011

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Images

Figure 1
(a) Schematic representation of $4 \times 4$ fluorographene supercell. Dark grey and light grey spheres represent C-F units with fluorine atoms above and below the fluorographene plane, respectively. Small filled circles show the most favorable adsorption sites for metallic atoms on FG, which are above the center of triangles formed by the three nearest fluorine atoms. Positions marked by opened circle and those directly above the fluorine atoms are less favorable. (b) Side view of fluorographene with an adsorbed metal atom.Reuse & Permissions
Figure 2
Electronic band structure of (a) fluorographene and (b) fluorographene with an adsorbed K atom. Red solid lines represent occupied states, while blue dashed lines represent empty states. The valence band maximum is set to zero. The Fermi level in (b) is shown with a black solid line and labeled as E $_{F}$ . Points labeled as A, B, and C are the points at which wave functions are calculated. The arrow points at the position of the potassium 4 $s^{1}$ level.Reuse & Permissions
Figure 3
Plot of the real part of the wave function for (a) fluorographene at point A in Fig. 2a and (b) for fluorographene with adsorbed K atom at point B in Fig. 2b. Carbon atoms are shown in dark grey color, while fluorine atoms are in green (light grey) color. Red and blue colors correspond to the different signs of the wave function. Note that the state in (a) is empty, while the same delocalized state is occupied in (b) showing that doping has occured.Reuse & Permissions
Figure 4
Plot of the real part of the wave function for the half-filled metallic level of fluorographene with the adsorbed K atom at (a) point B and (b) point C of the band structure shown in Fig. 2b. Carbon atoms are shown in dark grey color, while fluorine atoms are in green (light grey) color. Red and blue colors correspond to the different signs of the wave function.Reuse & Permissions
Figure 5
(a) Spin-up and (b) spin-down band structures for fluorographene with the adsorbed Au atom. Red solid lines represent occupied states, while blue dashed lines represent empty states. The valence band maximum is set to zero.Reuse & Permissions
Figure 6
(a) Molecular structure of F4-TCNQ and (b) F4-TCNQ on the top of fluorographene. Carbon atoms are shown in grey color. Fluorine and nitrogen atoms are represented with green and blue colors and labeled as F and N, respectively. (c) Electronic band structure of fluorographene with the F4-TCNQ molecule. Red solid lines represent occupied states, while blue dashed lines represent empty states. The valence band maximum is set to zero.Reuse & Permissions

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