Strong Electrostatic Control of Excitonic Features in MoS2 by a Free-Standing Ultrahigh-κ Ferroelectric Perovskite

Abstract

Integrating free-standing complex oxides with two-dimensional (2D) materials has recently attracted great interest, due to the rich physics evolving from such structures. Enhancing and tuning the opto–electronic properties of these systems is of high importance for a multitude of applications, such as sensors, memory devices or optical communications. The electrostatic control of photoluminescence of monolayer MoS2 at room temperature via integration of free-standing BaTiO3 (BTO), a ferroelectric perovskite oxide is presented. It is shown that the use of BTO leads to highly tunable exciton emission of MoS2 in a minimal range of gate voltages. Due to BTO's ferroelectric polarization-induced doping, large peak emission shifts as well as a large and tunable A trion binding energy in the range of 40–100 meV are observed. These measurements are compared with those carried out when the BTO is replaced by a hexagonal boron nitride (hBN) dielectric layer, confirming BTO's superior gating properties and thus lower power consumption. Additionally, advantage of the ferroelectric switching of BTO is taken by fabricating devices where the BTO layer is decoupled from the gate electrode with a SiO2 layer. Choosing to isolate the BTO allows to induce large remanent behavior of MoS2’s excitonic features.