Intrinsic electronic transport and thermoelectric power factor in n-type doped monolayer MoS2

Abstract

The electronic transport and thermoelectric properties in n -type doped monolayer MoS _2 are investigated by a parameter-free method based on first-principles calculations, electron–phonon coupling (EPC), and Boltzmann transport equation (BTE). Remarkably, the calculated electron mobility μ ∼ 47 cm ^2 V ^−1 s ^−1 and thermoelectric power factor σS ^2 ∼ 2.93 × 10 ^−3 W m ^−1 K ^−2 at room temperature are much lower than the previous theoretical values (e.g. μ ∼ 130–410 cm ^2 V ^−1 s ^−1 and σS ^2 ∼ 2.80 × 10 ^−2 W m ^−1 K ^−2 ), but agree well with the most recent experimental findings of μ ∼ 37 cm ^2 V ^−1 s ^−1 and σS ^2 ∼ 3.00 × 10 ^−3 W m ^−1 K ^−2 . The EPC projections on phonon dispersion and the phonon branch dependent scattering rates indicate that the acoustic phonons, especially the longitudinal acoustic phonons, dominate the carrier scattering. Therefore, a mobility of 68 cm ^2 V ^−1 s ^−1 is achieved if only the acoustic phonons induced scattering is included, in accordance with the result of 72 cm ^2 V ^−1 s ^−1 estimated from the deformation potential driven by acoustic modes. Furthermore, via excluding the scattering from the out-of-plane modes to simulate the EPC suppression, the obtained mobility of 258 cm ^2 V ^−1 s ^−1 is right in the range of 200–700 cm ^2 V ^−1 s ^−1 measured in the samples with top deposited dielectric layer. In addition, we also compute the lattice thermal conductivity κ _L of monolayer MoS _2 using phonon BTE, and obtain a κ _L ∼ 123 W m ^−1 K ^−1 at 300 K.

Keywords

• electron–phonon coupling
• electronic transport
• Boltzmann transport equation
• thermoelectric power factor
• thermal conductivity
• mobility