# Molecular Sieve Promoted Growth of Ferroelectric Trilayer 3R‐MoS2 for Polarization‐Dependent Reconfigurable Optoelectronic Synapses

## TL;DR

Researchers developed a new method to grow a special type of MoS2 crystal that can be used for reconfigurable optoelectronic devices, such as neuromorphic synapses.

## Contribution

A molecular sieve-assisted chemical vapor deposition method is introduced to synthesize 3R-MoS2 with enhanced ferroelectric properties.

## Key findings

- 3R-MoS2 nanoflakes exhibit switchable out-of-plane polarization and robust sliding ferroelectricity.
- The polarization state controls temporal photoresponse, enabling reconfigurable photocurrent behavior.
- 3R-MoS2 shows broadband optoelectronic synaptic plasticity under specific polarization states.

## Abstract

2D sliding ferroelectric semiconductors are a unique combination of switchable electric polarization and gate/light modulated charge transport, rendering them an appealing platform for multifunctional electronic and optoelectronic devices. However, the currently available 2D sliding ferroelectric semiconductors are limited, and the coupled gate‐light‐polarization interactions in such systems remain to be further explored. Herein, trilayer (3L) rhombohedral‐stacked (3R) MoS2 nanoflakes are synthesized via a molecular sieve‐assisted chemical vapor deposition strategy, in which the combined physical vapor buffer and chemical sodium release from the molecular sieves effectively promote vertical growth with a favorable 3R stacking configuration. The noncentrosymmetric crystal structure, switchable out‐of‐plane polarization, and robust sliding ferroelectricity are systematically characterized. Integrating 3L 3R‐MoS2 into ferroelectric semiconductor field‐effect transistors (FeS‐FETs) reveals a large polarization‐direction‐dependent memory window of 13.8–14.6 V. Moreover, the ferroelectric polarization state, reversibly controlled by the polarity of the gate voltage, strongly governs the temporal photoresponse, enabling reconfigurable progressive photocurrent depression or facilitation. Combined with its narrow bandgap and defect‐assisted absorption, a broadband optoelectronic synaptic plasticity was further evaluated under a specific polarization state. These results establish 3L 3R‐MoS2 as a highly promising 2D crystals for ferroelectric optoelectronic synapses and future in‐memory sensing systems.

The noncentrosymmetric trilayer rhombohedral‐stacked MoS2 nanoflakes with enhanced sliding ferroelectric properties are synthesized via a molecular sieve‐assisted chemical vapor deposition process. The switchable polarization states, combined with the exceptional light/gate voltage modulated electrical properties of these nanoflakes, enable broadband and reconfigurable neuromorphic optoelectronic synaptic devices.