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Tunable carrier multiplication and cooling in graphene
Jens Christian Johannsen1, Søren Ulstrup, Alberto Crepaldi
1Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL) , 1015 Lausanne, Switzerland.
Nano Letters
|December 3, 2014
Summary
Doping graphene affects how quickly hot carriers cool down after photoexcitation. Stronger n-doping leads to faster cooling and higher carrier multiplication in graphene, enabling control over its dynamical response.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Ultrafast Spectroscopy
Background:
- Graphene's unique electronic properties, particularly its Dirac cone, are sensitive to doping.
- Understanding carrier dynamics in graphene is crucial for optoelectronic applications.
Purpose of the Study:
- To investigate the influence of doping levels on ultrafast carrier dynamics in graphene.
- To explore the relationship between doping, carrier multiplication, and cooling rates.
Main Methods:
- Time- and angle-resolved photoemission spectroscopy (TARPS) was employed.
- Two doped graphene samples with distinct doping levels (n-type and p-type) were analyzed.
Main Results:
- Significant differences in hot carrier dynamics were observed between n- and p-doped graphene.
- Stronger n-doping exhibited higher carrier multiplication factors (>3).
- Faster phonon-mediated carrier cooling was detected in more strongly doped graphene.
Conclusions:
- Doping level is a critical parameter for manipulating graphene's ultrafast response to photoexcitation.
- Tuning doping offers a pathway to control carrier multiplication and cooling dynamics.
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