Electronic properties of few-layer MoS2 under an external electrical field

MoS$_2$ is a two-dimensional (2D) layered material with a band gap in the 1-2 eV range, depending on the number of layers, and with promising applications in nanoelectronics. Field-effect transistors based on MoS$_2$ have been fabricated, displaying room-temperature electron mobility of $~200 cm^{2}V^{-1}s^{-1}$ and high on/off ratios on the order of $10^{8}$. In these devices, the effect of the electric field across the MoS$_2$ layers is important for device operation, so understanding these effects will aid in improving device performance. Here we use first-principles calculations to determine the electronic properties of MoS$_2$ layers as a function of an electric field applied perpendicular to the layers, representing the effect of gate electrodes. In the absence of an external field, the valence and conduction bands of multilayer MoS$_2$ are degenerate. However, an applied external field generates a gradient potential inside the material, breaking the symmetry between the layers, lifting the degeneracies, and modifying the band gap. We will discuss the evolution of the band gap and the various minima in the conduction band as a function of the field intensity and the number of layers. Work supported by FAPESP and by NSF-IMI.