Interfacial ferroelectricity in marginally twisted 2D semiconductors

TL;DR

This paper reports the discovery of room-temperature ferroelectricity in twisted 2D MoS2 heterostructures, enabling new electronic devices with built-in memory through interfacial polarization control.

Contribution

It introduces a novel ferroelectric semiconductor based on twisted 2D heterostructures, demonstrating controllable ferroelectric domains and potential for electronic applications.

Findings

Ferroelectric domains with out-of-plane polarization are observed at room temperature.

Domain walls can be moved and manipulated using electric fields.

Hysteresis in channel resistance demonstrates ferroelectric memory effects.

Abstract

Twisted heterostructures of two-dimensional crystals offer almost unlimited scope for the design of novel metamaterials. Here we demonstrate a room-temperature ferroelectric semiconductor that is assembled using mono- or few- layer MoS2. These van der Waals heterostructures feature broken inversion symmetry, which, together with the asymmetry of atomic arrangement at the interface of two 2D crystals, enables ferroelectric domains with alternating out-of-plane polarisation arranged into a twist-controlled network. The latter can be moved by applying out-of-plane electrical fields, as visualized in situ using channelling contrast electron microscopy. The interfacial charge transfer for the observed ferroelectric domains is quantified using Kelvin probe force microscopy and agrees well with theoretical calculations. The movement of domain walls and their bending rigidity also agrees well with our modelling results. Furthermore, we demonstrate proof-of-principle field-effect transistors, where the channel resistance exhibits a pronounced hysteresis governed by pinning of ferroelectric domain walls. Our results show a potential venue towards room temperature electronic and optoelectronic semiconductor devices with built-in ferroelectric memory functions.