Limits...
Dopant morphology as the factor limiting graphene conductivity.

Hofmann M, Hsieh YP, Chang KW, Tsai HG, Chen TT - Sci Rep (2015)

Bottom Line: First the agglomeration of dopants into clusters provides a route to increase the graphene conductivity through formation of ordered scatterers.As the cluster grows, the charge transfer efficiency between graphene and additional dopants decreases due to emerging polarization effects.The presented results help identifying the range of beneficial doping density and guide the choice of suitable dopants for graphene's future applications.

View Article: PubMed Central - PubMed

Affiliation: Department of Material Science and Engineering, National Cheng Kung University, Tainan 70101, Taiwan.

ABSTRACT
Graphene's low intrinsic carrier concentration necessitates extrinsic doping to enhance its conductivity and improve its performance for application as electrodes or transparent conductors. Despite this importance limited knowledge of the doping process at application-relevant conditions exists. Employing in-situ carrier transport and Raman characterization of different dopants, we here explore the fundamental mechanisms limiting the effectiveness of doping at different doping levels. Three distinct transport regimes for increasing dopant concentration could be identified. First the agglomeration of dopants into clusters provides a route to increase the graphene conductivity through formation of ordered scatterers. As the cluster grows, the charge transfer efficiency between graphene and additional dopants decreases due to emerging polarization effects. Finally, large dopant clusters hinder the carrier motion and cause percolative transport that leads to an unexpected change of the Hall effect. The presented results help identifying the range of beneficial doping density and guide the choice of suitable dopants for graphene's future applications.

No MeSH data available.


Related in: MedlinePlus

Transport at high coverage (a) Hall resistance vs. sheet resistance at low and high coverage (inset) EFM image of adsorbates at high coverage, (b) transport after suppression of percolation by formation of adsorbate super lattice, (inset) micrograph of microsphere array.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4663794&req=5

f4: Transport at high coverage (a) Hall resistance vs. sheet resistance at low and high coverage (inset) EFM image of adsorbates at high coverage, (b) transport after suppression of percolation by formation of adsorbate super lattice, (inset) micrograph of microsphere array.

Mentions: We now turn to the high doping concentration regime. EFM imaging in this range reveals that clusters have extended far enough to merge with neighboring clusters (inset of Fig. 4(a)). In this case two continuous phases exist – graphene and adsorbate-covered graphene. Due to the previously mentioned electric fields at the interface of these two regions, barriers exist that prevent charge transport between them. Instead, percolative carrier transport will proceed mainly through one region.


Dopant morphology as the factor limiting graphene conductivity.

Hofmann M, Hsieh YP, Chang KW, Tsai HG, Chen TT - Sci Rep (2015)

Transport at high coverage (a) Hall resistance vs. sheet resistance at low and high coverage (inset) EFM image of adsorbates at high coverage, (b) transport after suppression of percolation by formation of adsorbate super lattice, (inset) micrograph of microsphere array.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663794&req=5

f4: Transport at high coverage (a) Hall resistance vs. sheet resistance at low and high coverage (inset) EFM image of adsorbates at high coverage, (b) transport after suppression of percolation by formation of adsorbate super lattice, (inset) micrograph of microsphere array.
Mentions: We now turn to the high doping concentration regime. EFM imaging in this range reveals that clusters have extended far enough to merge with neighboring clusters (inset of Fig. 4(a)). In this case two continuous phases exist – graphene and adsorbate-covered graphene. Due to the previously mentioned electric fields at the interface of these two regions, barriers exist that prevent charge transport between them. Instead, percolative carrier transport will proceed mainly through one region.

Bottom Line: First the agglomeration of dopants into clusters provides a route to increase the graphene conductivity through formation of ordered scatterers.As the cluster grows, the charge transfer efficiency between graphene and additional dopants decreases due to emerging polarization effects.The presented results help identifying the range of beneficial doping density and guide the choice of suitable dopants for graphene's future applications.

View Article: PubMed Central - PubMed

Affiliation: Department of Material Science and Engineering, National Cheng Kung University, Tainan 70101, Taiwan.

ABSTRACT
Graphene's low intrinsic carrier concentration necessitates extrinsic doping to enhance its conductivity and improve its performance for application as electrodes or transparent conductors. Despite this importance limited knowledge of the doping process at application-relevant conditions exists. Employing in-situ carrier transport and Raman characterization of different dopants, we here explore the fundamental mechanisms limiting the effectiveness of doping at different doping levels. Three distinct transport regimes for increasing dopant concentration could be identified. First the agglomeration of dopants into clusters provides a route to increase the graphene conductivity through formation of ordered scatterers. As the cluster grows, the charge transfer efficiency between graphene and additional dopants decreases due to emerging polarization effects. Finally, large dopant clusters hinder the carrier motion and cause percolative transport that leads to an unexpected change of the Hall effect. The presented results help identifying the range of beneficial doping density and guide the choice of suitable dopants for graphene's future applications.

No MeSH data available.


Related in: MedlinePlus