Manzhang

Twisted bilayer transitionmetal dichalcogenides provide a unique platform for investigating intriguing fundamental physical properties. A tilted SiO₂/Si substrate is introduced into chemical vapordeposition to synthesize twisted bilayer WS₂ with a wide twist angle range from 0° to 120°. The strong correlation between the SHG response and the twist angle suggests atunable SHG performance with twist angles.

Abstract

The introduction of rotational freedom by twist angles in twisted bilayer (TB) transition metal dichalcogenides (TMDCs) can tailor the inherent properties of the TMDCs, which provides a promising platform to investigate the exotic physical properties. However, direct synthesis of high-quality TB-TMDCs with full twist angles is significantly challenging due to the substantial energy barriers during crystal growth. Here, a modified chemical vapor deposition strategy is proposed to synthesize TB-WS₂ with a wide twist angle range from 0° to 120°. Utilizing a tilted SiO₂/Si substrate, a gas flow disturbance is generated in the furnace tube to create a heterogeneous concentration gradient of the metal precursor, which provides an extra driving force for the growth of TB-WS₂. The Raman and photoluminescence results confirm a weak interlayer coupling of the TB-WS₂. High-quality periodic Moiré patterns are observed in the scanning transmission electron microscopy images. Moreover, owing to the strong correlation between the nonlinear optical response and the twisted crystal structure, tunable second harmonic generation behaviors are realized in the TB-WS₂. This approach opens up a new avenue for the direct growth of high-crystalline-quality and pristine TB-TMDCs and their potential applications in nonlinear optical devices.

Nature Communications, Published online: 17 January 2024; doi:10.1038/s41467-023-44598-w

Twisted bilayers of 2D semiconductors are being intensively investigated due to their emergent physical properties, but their controlled bottom-up synthesis remains challenging. Here, the authors report a confined-space chemical vapour deposition strategy to synthesize MoS2 bilayers with twist angles ranging from 0° to 120°.

Nature Communications, Published online: 27 October 2023; doi:10.1038/s41467-023-42645-0

Here, the authors investigate frequently observed variations in data between different electrochemical cells using in-situ electronic/electrochemical measurements, developing a vertical microcell strategy to eliminate the conductance issue and enhance measurement reproducibility.