title: High thermoelectricpower factor in graphene/hBN devices.
abstract: Fast and controllable cooling at nanoscales requires a combination of highly efficient passive cooling and active cooling. Although passive cooling in graphene-based devices is quite effective due to graphene's extraordinary heat conduction, active cooling has not been considered feasible due to graphene's low thermoelectric power factor. Here, we show that the thermoelectric performance of graphene can be significantly improved by using hexagonal boron nitride (hBN) substrates instead of SiO2We find the room temperature efficiency of active cooling in the device, as gauged by the power factor times temperature, reaches values as high as 10.35 W⋅m-1⋅K-1, corresponding to more than doubling the highest reported room temperature bulk power factors, 5 W⋅m-1⋅K-1, in YbAl3, and quadrupling the best 2D power factor, 2.5 W⋅m-1⋅K-1, in MoS2We further show that the Seebeck coefficient provides a direct measure of substrate-induced random potential fluctuations and that their significant reduction for hBN substrates enables fast gate-controlled switching of the Seebeck coefficient polarity for applications in integrated active cooling devices.
authors.affiliation: Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854.|Department of Mechanical and Aerospace Engineering, Rutgers University, Piscataway, NJ 08854.|Institute of Advanced Materials, Devices, and Nanotechnology, Rutgers University, Piscataway, NJ 08854.
authors.forename: Junxi
authors.initials: J
authors.lastname: Duan
authors.affiliation: Department of Mechanical and Aerospace Engineering, Rutgers University, Piscataway, NJ 08854.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854.
authors.forename: Xinyuan
authors.initials: X
authors.lastname: Lai
authors.affiliation: Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854.
authors.forename: Guohong
authors.initials: G
authors.lastname: Li
authors.affiliation: Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: Kenji
authors.identifier: 0000-0003-3701-8119
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Taniguchi
authors.affiliation: Department of Mechanical and Aerospace Engineering, Rutgers University, Piscataway, NJ 08854; eandrei@physics.rutgers.edu m.zebarjadi@virginia.edu.|Institute of Advanced Materials, Devices, and Nanotechnology, Rutgers University, Piscataway, NJ 08854.
authors.forename: Mona
authors.initials: M
authors.lastname: Zebarjadi
authors.affiliation: Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854; eandrei@physics.rutgers.edu m.zebarjadi@virginia.edu.|Institute of Advanced Materials, Devices, and Nanotechnology, Rutgers University, Piscataway, NJ 08854.
authors.forename: Eva Y
authors.initials: EY
authors.lastname: Andrei
keywords: Seebeck coefficient; electron–hole puddles; graphene; screened Coulomb scattering; thermoelectric power factor