Phonon-limited mobility inn-type single-layer MoS2from first principles

Abstract

We study the phonon-limited mobility in intrinsic n-type single-layer MoS2 for temperatures T > 100 K. The materials properties including the electron-phonon interaction are calculated from first-principles and the deformation potentials and Fröhlich interaction in single-layer MoS2 are established. The calculated room-temperature mobility of ∼ 410 cm 2 V −1 s −1 is found to be dominated by optical phonon scattering via intra and intervalley deformation potential couplings and the Fröhlich interaction. The mobility is weakly dependent on the carrier density and follows a µ ∼ T −γ temperature dependence with γ = 1.69 at room temperature. It is shown that a quenching of the characteristic homopolar mode which is likely to occur in top-gated samples, increases the mobility with ∼ 70 cm 2 V −1 s −1 and can be observed as a decrease in the exponent to γ = 1.52. In comparison to recent experimental findings for the mobility in single-layer MoS2 (∼ 200 cm 2 V −1 s −1 ), our results indicate that mobilities close to the intrinsic phonon-limited mobility can be achieved in two-dimensional materials via dielectric engineering that effectively screens static Coulomb scattering on e.g. charged impurities.

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides

“…Additionally, freestanding MoS 2 has been shown to have similar ripples 113 to those in graphene, which may also contribute to scattering and mobility reduction. The phonon-limited roomtemperature mobility calculated by Kaasbjerg et al 104 -1 (refs 1,11).…”

“…Carrier mobility is increasingly affected by phonon scattering with increasing temperature 104 . In 2D TMDCs, which have partially ionic bonds between the metal and chalcogen atoms, crystal deformation leads to polarization fields that can interact with and scatter electrons.…”

“…In 2D TMDCs, which have partially ionic bonds between the metal and chalcogen atoms, crystal deformation leads to polarization fields that can interact with and scatter electrons. Figure 3c shows the temperature dependence of electron mobility in single-layer MoS 2 calculated from first principles by Kaasbjerg et al 104 . The mobility due to acoustic phonon scattering alone is shown along with the total effect of acoustic and optical phonon scattering.…”

“…3c). The room-temperature mobility is limited to ~410 cm 2 V -1 s -1 , primarily owing to optical phonons 104 .…”

“…By considering the mean free path of carriers, the impurity concentration required to make impurity scattering dominant over phonon scattering is calculated to be ~5 × 10 11 cm -2 , which corresponds to heavy doping 104 . These results show that the improvement in room-temperature mobility from ~0.5-3 cm 2 V -1 s -1 in earlier reports 1,11 of MoS 2 transistors to ~200 cm 2 V -1 s -1 more recently 34 is primarily due to the dielectric screening of Coulomb scattering on charged impurities by using gate dielectric materials with a high dielectric constant.…”