Mobility enhancement and temperature dependence in top-gated single-layer MoS2

Abstract

The deposition of a high-$\kappa$ oxide overlayer is known to significantly enhance the room-temperature electron mobility in single-layer MoS${}_2$ (SLM) but not in single-layer graphene (SLG). We give a quantitative account of how this mobility enhancement is due to the non-degeneracy of the two-dimensional electron gas system in SLM at accessible temperatures. Using our charged impurity scattering model [Ong and Fischetti, Phys. Rev. B 86, 121409 (2012)] and temperature-dependent polarizability, we calculate the charged impurity-limited mobility (${\mu }_{\text{imp}}$) in SLM with and without a high-$\kappa$ (HfO${}_2$) top gate oxide at different electron densities and temperatures. We find that the mobility enhancement is larger at low electron densities and high temperatures because of finite-temperature screening, thus explaining the enhancement of the mobility observed at room temperature. ${\mu }_{\text{imp}}$ is shown to decrease significantly with increasing temperature, suggesting that the strong temperature dependence of measured mobilities should not be interpreted as being solely due to inelastic scattering with phonons. We also reproduce the recently seen experimental trend in which the temperature scaling exponent ($\gamma$) of ${\mu }_{\text{imp}}\propto T^{-\gamma }$ is smaller in top-gated SLM than in bare SLM. Finally, we show that a $\sim 37$ percent mobility enhancement can be achieved by reducing the HfO${}_2$ thickness from 20 to 2 nm.

8 pages, 6 figures

References in corpus (7)

• Electric Field Effect in Atomically Thin Carbon Films
• Substrate-induced band gap opening in epitaxial graphene
• Realization of a High Mobility Dual-gated Graphene Field Effect Transistor with Al2O3 Dielectric
• Substrate limited electron dynamics in graphene
• Screening induced temperature dependent transport in 2D graphene
• Origin of the energy bandgap in epitaxial graphene
• Theory of charged impurity scattering in two dimensional graphene

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• Epitaxial Growth of Large Area Single-Crystalline Few-Layer MoS2 with Room Temperature Mobility of 192 cm2V-1s-1
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