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Thermoelectric Power in Bilayer Graphene Device with Ionic Liquid Gating
Yung-Yu Chien1, Hongtao Yuan2, Chang-Ran Wang1
1Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan.
Scientific Reports
|February 9, 2016
Summary
Researchers enhanced thermoelectric power in bilayer graphene devices by using ionic-liquid gating to tune the band gap. This method significantly reduced charge puddles, improving transport properties and boosting thermoelectric performance by 40%.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Thermoelectric materials are crucial for energy harvesting and cooling applications, with a continuous search for materials exhibiting high thermoelectric power and figure of merit (ZT).
- Bilayer graphene presents tunable electronic properties, making it a promising candidate for advanced thermoelectric devices.
- Ionic liquid gating offers a method for electrostatic control of carrier density and electronic properties in 2D materials.
Purpose of the Study:
- To investigate the feasibility of tuning the band gap in bilayer graphene using ionic liquid gating.
- To enhance the thermoelectric power of bilayer graphene devices.
- To understand and mitigate the impact of charge puddles on transport properties at low temperatures.
Main Methods:
- Fabrication of bilayer graphene devices.
- Application of ionic liquid gating to tune the band gap via a perpendicular electric field.
- Measurement of thermoelectric power and transport properties at low temperatures.
- Control of Fermi level at the charge neutral point during cool-down to minimize charge puddles.
Main Results:
- A band gap of approximately 36.6 ± 3 meV was successfully formed in bilayer graphene at specific gate voltages (Vig = -1 V, Vbg = +23 V).
- A significant enhancement of nearly 40% in thermoelectric power was observed at 120 K.
- Reduction of the charge puddle effect was achieved by maintaining the Fermi level at the charge neutral point during cool-down, leading to improved low-temperature transport properties.
Conclusions:
- Ionic liquid gating is a viable technique for tuning the band gap in bilayer graphene.
- The observed enhancement in thermoelectric power demonstrates the potential of gated bilayer graphene for thermoelectric applications.
- Minimizing charge puddles is critical for optimizing the performance of ionic-liquid-gated graphene devices at low temperatures.
