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Related Experiment Video

Updated: Sep 7, 2025

Fabricating van der Waals Heterostructures with Precise Rotational Alignment

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Published on: July 5, 2019

Band Alignment Engineering by Twist Angle and Composition Modulation for Heterobilayer.

Ting Kang¹, Zijing Jin², Xu Han²

¹Department of Chemical and Biological Engineering, Guangdong-Hong Kong-Macao Joint Laboratory for Intelligent Micro-Nano Optoelectronic Technology, William Mong Institute of Nano Science and Technology, and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, 999077, P. R. China.

Small (Weinheim an Der Bergstrasse, Germany)

|June 23, 2022

Summary

Engineered transition metal dichalcogenide (TMD) heterobilayers show tunable band alignment for advanced optoelectronics. Strategies like alloy composition and twist angle control enhance photoluminescence and device performance.

Keywords:

alloys chemical vapor deposition heterobilayers transition metal dichalcogenides

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Area of Science:

Materials Science
Condensed Matter Physics
Nanotechnology

Background:

Atomically thin transition metal dichalcogenides (TMDs) possess direct band gaps and strong light-matter interactions, making them suitable for optoelectronic devices.
Efficient band alignment engineering is crucial for expanding the applications of TMDs in versatile optoelectronics.

Purpose of the Study:

To develop and demonstrate effective methods for tuning the band alignment of vertically stacked monolayer TMDs.
To explore the impact of alloy composition and twist angle on the electronic and optical properties of TMD heterobilayers.

Main Methods:

Utilized chemical vapor deposition (CVD) to synthesize vertically stacked monolayer TMDs.
Engineered band alignment through two primary strategies: formulating MoS_2(1-x)Se_2x alloy compositions and varying twist angles in heterobilayers.
Combined photoluminescence (PL) spectroscopy with density functional theory (DFT) calculations to analyze band alignment and optical properties.

Main Results:

Achieved continuously tunable band alignment and observed transitions between type II-type I-type II alignments by altering alloy composition.
Observed a significant photoluminescence enhancement (28%-110%) at moderate twist angles (10°-50°) due to type I alignment, indicating a coupling between twist angle and global band structure.
Demonstrated a heterojunction device (MoS_0.76Se_1.24/WS₂ with 14° twist) exhibiting high photoresponsivity (55.9 A W^-1), detectivity (1.07 × 10¹⁰ Jones), and external quantum efficiency (135%).

Conclusions:

Alloy composition and twist angle serve as effective engineering tools for controlling band alignment in TMD heterobilayers.
The demonstrated methods provide pathways for designing advanced heterostructures for high-performance optoelectronic devices.
The study highlights the potential of engineered TMD heterobilayers for next-generation photodetectors and other optoelectronic applications.