Strong electrostatic control of excitonic features in MoS$_2$ by a free-standing ultrahigh-$\kappa$ ferroelectric perovskite

TL;DR

This study demonstrates the electrostatic tuning of excitonic features in monolayer MoS$_2$ using a free-standing ferroelectric BaTiO$_3$ layer, enabling large, tunable shifts and hysteretic control of exciton and trion emissions at room temperature.

Contribution

It introduces a novel approach of integrating free-standing ferroelectric BaTiO$_3$ with MoS$_2$ for highly tunable and hysteretic excitonic control, surpassing traditional dielectric gating methods.

Findings

Large tunable exciton and trion emission shifts achieved.

Ferroelectric polarization induces significant doping effects.

Hysteretic behavior observed in excitonic features with ferroelectric switching.

Abstract

We present the electrostatic control of photoluminescence of monolayer MoS$_2$ at room temperature via integration of free-standing BaTiO$_3$ (BTO), a ferroelectric perovskite oxide, layers. We show that the use of BTO leads to highly tunable exciton emission of MoS$_2$ in a minimal range of gate voltages, effectively controlling the neutral excitons to charged excitons (trions) conversion. Due to BTO's ferroelectric polarization-induced doping we observe large peak emission shifts as well as a large and tunable A trion binding energy in the range of 40-100 meV. To further investigate the efficacy of electrostatic control, we compared our measurements with those carried out when the BTO is replaced by a hexagonal boron nitride (hBN) dielectric layer of comparable thickness, confirming BTO's superior gating properties and thus lower power consumption. Additionally, we take advantage of the ferroelectric switching of BTO by fabricating devices where the BTO layer is decoupled from the gate electrode with a SiO$_2$ layer. Choosing to isolate the BTO allows us to induce large remanent behavior of MoS$_2$'s excitonic features, observing hysteretic behavior in the peak energy ratio between A exciton and its trion, as well as hysteretic behavior in the doping-related trion energy shift. This study illustrates the rich physics involved in combining free-standing complex oxide layers with two-dimensional materials.