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

Cluster formation: (a) log-log-plot of carrier mobility vs. carrier density for different dopants, (b) EFM before ozone exposure, (c) EFM after short exposure on same color scale.
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f2: Cluster formation: (a) log-log-plot of carrier mobility vs. carrier density for different dopants, (b) EFM before ozone exposure, (c) EFM after short exposure on same color scale.

Mentions: Figure 2(a) shows a plot of mobility vs. carrier density for short dopant exposures on a log-log scale. Assuming that the carrier concentration is proportional to the impurity concentration n~nrandom and using the above description, a slope of −1 would be expected for both Coulombic scatterers and short range scatterers in such a plot. Instead, we observe slopes smaller than −1 for all three dopants. This behavior indicates that the mobility is less affected by an increase in scatterer concentration than the carrier density.


Dopant morphology as the factor limiting graphene conductivity.

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

Cluster formation: (a) log-log-plot of carrier mobility vs. carrier density for different dopants, (b) EFM before ozone exposure, (c) EFM after short exposure on same color scale.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: Cluster formation: (a) log-log-plot of carrier mobility vs. carrier density for different dopants, (b) EFM before ozone exposure, (c) EFM after short exposure on same color scale.
Mentions: Figure 2(a) shows a plot of mobility vs. carrier density for short dopant exposures on a log-log scale. Assuming that the carrier concentration is proportional to the impurity concentration n~nrandom and using the above description, a slope of −1 would be expected for both Coulombic scatterers and short range scatterers in such a plot. Instead, we observe slopes smaller than −1 for all three dopants. This behavior indicates that the mobility is less affected by an increase in scatterer concentration than the carrier density.

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