title: Gate-Tuned Thermoelectric Power in Black Phosphorus.
abstract: The electric field effect is a useful means of elucidating intrinsic material properties as well as for designing functional devices. The electric-double-layer transistor (EDLT) enables the control of carrier density in a wide range, which is recently proved to be an effective tool for the investigation of thermoelectric properties. Here, we report the gate-tuning of thermoelectric power in a black phosphorus (BP) single crystal flake with the thickness of 40 nm. Using an EDLT configuration, we successfully control the thermoelectric power (S) and find that the S of ion-gated BP reached +510 μV/K at 210 K in the hole depleted state, which is much higher than the reported bulk single crystal value of +340 μV/K at 300 K. We compared this experimental data with the first-principles-based calculation and found that this enhancement is qualitatively explained by the effective thinning of the conduction channel of the BP flake and nonuniformity of the channel owing to the gate operation in a depletion mode. Our results provide new opportunities for further engineering BP as a thermoelectric material in nanoscale.
authors.affiliation: Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo , Tokyo 113-8656, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Saito
authors.affiliation: Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo , Tokyo 113-8656, Japan.
authors.forename: Takahiko
authors.initials: T
authors.lastname: Iizuka
authors.affiliation: RIKEN Center for Emergent Matter Science (CEMS) , Wako 351-0198, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Koretsune
authors.affiliation: RIKEN Center for Emergent Matter Science (CEMS) , Wako 351-0198, Japan.
authors.forename: Ryotaro
authors.initials: R
authors.lastname: Arita
authors.affiliation: RIKEN Center for Emergent Matter Science (CEMS) , Wako 351-0198, Japan.
authors.forename: Sunao
authors.initials: S
authors.lastname: Shimizu
authors.affiliation: Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo , Tokyo 113-8656, Japan.|RIKEN Center for Emergent Matter Science (CEMS) , Wako 351-0198, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Iwasa
keywords: Black phosphorus; Seebeck coefficient; electric-double-layer transistor (EDLT); gate-tuning; thermoelectric power