Transport and field emission properties of MoS2 bilayers

Abstract

We report the electrical characterization and field emission properties of MoS2 bilayers deposited on a SiO2/Si substrate. Current–voltage characteristics are measured in the back-gate transistor configuration, with Ti contacts patterned by electron beam lithography. We confirm the n-type character of as-grown MoS2 and we report normally-on field-effect transistors. Local characterization of field emission is performed inside a scanning electron microscope chamber with piezo-controlled tungsten tips working as the anode and the cathode. We demonstrate that an electric field of ~200 V/μm is able to extract current from the flat part of MoS2 bilayers, which can therefore be conveniently exploited for field emission applications even in low field enhancement configurations. We show that a Fowler–Nordheim model, modified to account for electron confinement in two-dimensional (2D) materials, fully describes the emission process.