Effect of doping and strain modulations on electron transport in monolayerMoS2

Abstract

The doping and strain effects on the electron transport of monolayer MoS2 are systematically investigated using the first-principles calculations with Boltzmann transport theory. We estimate the mobility has a maximum 275 cm 2 /(V·s) in the low doping level under the strain-free condition. The applying a small strain (∼3%) can improve the maximum mobility to 1150 cm 2 /(V·s) and the strain effect is more significant in the high doping level. We demonstrate that the electric resistance mainly due to the electron transition between K and Q valleys scattered by the M momentum phonons. However, the strain can effectively suppress this type of electronphonon coupling by changing the energy difference between the K and Q valleys. This sensitivity of mobility to the external strain may direct the improving electron transport of MoS2.

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

“…As shown in figure 2, both the mobility μ and conductivity σ decrease with the increasing T at the same n, consistent with the change of SRs versus T. At the same T, in contrast to the decrease of mobility μ versus n, the conductivity σ increases with n due to the enhancement of EDOS. At room temperature, the calculated maximum value of the electron mobility is μ∼47 cm 2 V −1 s −1 , which is much lower than the theoretical values of 130-410 cm 2 V −1 s −1 [17][18][19][20]. Compared with the experimental data, this result is in agreement with the most recent finding of 37 cm 2 V −1 s −1 [22], although it is much higher than the early data in the range of 0.5-3 cm 2 V −1 s −1 [8] and much lower than the values of 200-700 cm 2 V −1 s −1 [7,[14][15][16].…”

“…However, the deformation potential theory based on only the acoustic phonon scattering mechanism indicates that monolayer MoS 2 possesses an electron mobility of 72 cm 2 V −1 s −1 [21]. In view of further decrease of the mobility by inclusion of optical phonon scattering, this result is in sharp contrast to the theoretical values above 130 cm 2 V −1 s −1 [17][18][19][20]. Moreover, a most recent experimental measure on monolayer MoS 2 shows a small electron mobility of only 37 cm 2 V −1 s −1 at room temperature [22], and a prior Hall measurement exhibits a mobility of only 64 cm 2 V −1 s −1 at 260 K [23].…”

“…The energetically stable monolayer MoS 2 is the H 2 phase with the symmetry D h 3 , in which a molybdenum (Mo) layer is sandwiched between two sulfur (S) layers, as sketched in figure 1(a). Since the largest effective thermoelectric power factor σS 2 is captured around a small electron doping concentration n∼6.0×10 12 cm −2 (corresponding to about 0.005e per unit cell) [22] and the band structure and phonon dispersion have almost no change induced by such weak doping [13,19], the rigid band model of the undoped monolayer MoS 2 is sufficient to study the EPC and carrier scattering rates (SRs). Hence, unless otherwise stated, we take the undoped H 2 phase and the rigid band model to study the transport properties of n-type doped monolayer MoS 2 in this paper.…”

“…Much higher mobilities of 200-700 cm 2 V −1 s −1 can be reached through high-κ gate dielectric engineering to effectively screen the charged-impurities scattering and suppress the electron-phonon scattering [7,[14][15][16]. Theoretically, the phonon-mediated intrinsic mobilities have been calculated to be 130-410 cm 2 V −1 s −1 at room temperature according to the full band Monte Carlo simulations, EPC matrix calculations, or the deformation potential couplings in combination of Fröhlich interactions [17][18][19][20]. However, the deformation potential theory based on only the acoustic phonon scattering mechanism indicates that monolayer MoS 2 possesses an electron mobility of 72 cm 2 V −1 s −1 [21].…”

Linear magnetotransport in monolayerMoS2

“…This value of mobility, though one order larger than those currently obtained experimentally, 11,13 is consistent with the theoretical work. 15 Higher linear mobility at low temperature can be achieved via the gate dielectric engineering to effectively screen charge impurities, 44 and doping and strain modulations already realized a mobility higher than 1000 cm 2 /Vs at room temperature, 45 we thus expect this zero-temperature mobility will be reached in the near As can be seen from Fig. 1, the magnetoresistivity versus filling factor ν 0 or magnetic field B, exhibits marked SdHO with a beating pattern, having approximate period ∆ν 0 ≃ 1 at large fillings or low magnetic fields.…”