Charge transport in ion-gated mono-, bi-, and trilayer MoS2 field effect transistors

Charge transport in MoS2 in the low carrier density regime is dominated by trap states and band edge disorder. The intrinsic transport properties of MoS2 emerge in the high density regime where conduction occurs via extended states. Here, we investigate the transport properties of mechanically exfoliated mono-, bi-, and trilayer MoS2 sheets over a wide range of carrier densities realized by a combination of ion gel top gate and SiO2 back gate, which allows us to achieve high charge carrier (>10(13) cm(-2)) densities. We discuss the gating properties of the devices as a function of layer thickness and demonstrate resistivities as low as 1 k Omega for monolayer and 420 Omega for bilayer devices at 10 K. We show that from the capacitive coupling of the two gates, quantum capacitance can be roughly estimated to be on the order of 1 mu F/cm(2) for all devices studied. The temperature dependence of the carrier mobility in the high density regime indicates that short-range scatterers limit charge transport at low temperatures.