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Doping graphene films via chemically mediated charge transfer.

Ishikawa R, Bando M, Morimoto Y, Sandhu A - Nanoscale Res Lett (2011)

Bottom Line: Graphene-based TCFs have attracted a lot of attention because of their high electrical conductivity, transparency, and low cost.Notably, TCNQ is well known as a powerful electron accepter and is expected to favor electron transfer from graphene into TCNQ molecules, thereby leading to p-type doping of graphene films.Small amounts of TCNQ drastically improved the resistivity without degradation of optical transparency.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro, Tokyo 152-8552, Japan. ishikawa.r.ab@m.titech.ac.jp.

ABSTRACT
Transparent conductive films (TCFs) are critical components of a myriad of technologies including flat panel displays, light-emitting diodes, and solar cells. Graphene-based TCFs have attracted a lot of attention because of their high electrical conductivity, transparency, and low cost. Carrier doping of graphene would potentially improve the properties of graphene-based TCFs for practical industrial applications. However, controlling the carrier type and concentration of dopants in graphene films is challenging, especially for the synthesis of p-type films. In this article, a new method for doping graphene using the conjugated organic molecule, tetracyanoquinodimethane (TCNQ), is described. Notably, TCNQ is well known as a powerful electron accepter and is expected to favor electron transfer from graphene into TCNQ molecules, thereby leading to p-type doping of graphene films. Small amounts of TCNQ drastically improved the resistivity without degradation of optical transparency. Our carrier doping method based on charge transfer has a huge potential for graphene-based TCFs.

No MeSH data available.


Physical property of fabricated doped graphene films. (a) Optical transmittance spectra, (b) Summarized optical and electrical properties.
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Figure 7: Physical property of fabricated doped graphene films. (a) Optical transmittance spectra, (b) Summarized optical and electrical properties.

Mentions: Figure 7a shows optical transmittance spectra of doped and undoped graphene films at the same spray volumes. Except for an appearance of slight adsorption around 500 nm, spectrum did not change dominantly after doping. Transmittance (at 550 nm) as a function of sheet resistance of doped and undoped graphene films is summarized in Figure 7b. Owing to carrier doping from TCNQ, the sheet resistance drastically decreased by two orders of magnitude without degradation of optical transparency. To the best of our knowledge, such drastic doping effects have never been achieved until now [20]. However, the estimated sheet carrier concentrations were 9.96 × 1010 and 1.17 × 1012 cm-2 for the undoped and doped graphenes, respectively. These estimated values are similar to the reported values by Coletti et al. [21]. They modified the carrier concentration of monolayer epitaxial graphene on SiC by one order of magnitude by deposition of tetrafluoro-TCNQ. In short, the better doping effect cannot be interpreted only by accelerated charge transfer induced by radicalized TCNQ molecules in DMF solvent. Further it is necessary to consider other factors such as improvement of film stacking or percolation effect.


Doping graphene films via chemically mediated charge transfer.

Ishikawa R, Bando M, Morimoto Y, Sandhu A - Nanoscale Res Lett (2011)

Physical property of fabricated doped graphene films. (a) Optical transmittance spectra, (b) Summarized optical and electrical properties.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211156&req=5

Figure 7: Physical property of fabricated doped graphene films. (a) Optical transmittance spectra, (b) Summarized optical and electrical properties.
Mentions: Figure 7a shows optical transmittance spectra of doped and undoped graphene films at the same spray volumes. Except for an appearance of slight adsorption around 500 nm, spectrum did not change dominantly after doping. Transmittance (at 550 nm) as a function of sheet resistance of doped and undoped graphene films is summarized in Figure 7b. Owing to carrier doping from TCNQ, the sheet resistance drastically decreased by two orders of magnitude without degradation of optical transparency. To the best of our knowledge, such drastic doping effects have never been achieved until now [20]. However, the estimated sheet carrier concentrations were 9.96 × 1010 and 1.17 × 1012 cm-2 for the undoped and doped graphenes, respectively. These estimated values are similar to the reported values by Coletti et al. [21]. They modified the carrier concentration of monolayer epitaxial graphene on SiC by one order of magnitude by deposition of tetrafluoro-TCNQ. In short, the better doping effect cannot be interpreted only by accelerated charge transfer induced by radicalized TCNQ molecules in DMF solvent. Further it is necessary to consider other factors such as improvement of film stacking or percolation effect.

Bottom Line: Graphene-based TCFs have attracted a lot of attention because of their high electrical conductivity, transparency, and low cost.Notably, TCNQ is well known as a powerful electron accepter and is expected to favor electron transfer from graphene into TCNQ molecules, thereby leading to p-type doping of graphene films.Small amounts of TCNQ drastically improved the resistivity without degradation of optical transparency.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro, Tokyo 152-8552, Japan. ishikawa.r.ab@m.titech.ac.jp.

ABSTRACT
Transparent conductive films (TCFs) are critical components of a myriad of technologies including flat panel displays, light-emitting diodes, and solar cells. Graphene-based TCFs have attracted a lot of attention because of their high electrical conductivity, transparency, and low cost. Carrier doping of graphene would potentially improve the properties of graphene-based TCFs for practical industrial applications. However, controlling the carrier type and concentration of dopants in graphene films is challenging, especially for the synthesis of p-type films. In this article, a new method for doping graphene using the conjugated organic molecule, tetracyanoquinodimethane (TCNQ), is described. Notably, TCNQ is well known as a powerful electron accepter and is expected to favor electron transfer from graphene into TCNQ molecules, thereby leading to p-type doping of graphene films. Small amounts of TCNQ drastically improved the resistivity without degradation of optical transparency. Our carrier doping method based on charge transfer has a huge potential for graphene-based TCFs.

No MeSH data available.