Wafer-Scale Single-Crystal WSe₂ Monolayers Using Substrate-Passivation-Driven Epitaxy

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) are crucial for next-generation electronics and optoelectronics due to their subnanometer thickness and unique functionalities.
• P-type TMDs, like tungsten diselenide (WSe2), are essential for complementary metal-oxide-semiconductor (CMOS) 2D circuits, but achieving wafer-scale, single-orientation monolayers remains a significant challenge compared to n-type materials.
• Existing methods struggle to produce large-area, highly oriented p-type TMD monolayers, hindering their integration into advanced electronic devices.

Purpose of the Study:

• To develop a robust strategy for producing wafer-scale, single-orientation p-type WSe2 monolayers.
• To overcome the limitations in achieving high-quality, oriented p-type TMDs for scalable 2D electronic applications.
• To establish a materials platform that bridges the performance gap between n-type and p-type 2D semiconductors.

Main Methods:

• Implementation of a substrate-passivation-driven epitaxy strategy.
• In situ substrate treatment involving precise control over the introduction sequence of H2 gas and Se vapor.
• Engineering of an AlOSe2-Se-passivated sapphire surface to stabilize the WSe2 monolayer growth.
• Growth of WSe2 monolayers on a two-inch C-plane sapphire substrate.

Main Results:

• Achieved a 98.44% single-orientation WSe2 monolayer on a two-inch C-plane sapphire substrate, significantly surpassing previous benchmarks (82-87%).
• The engineered passivation layer stabilized the WSe2 monolayer with a predominantly 30° single orientation.
• Optical and electrical characterization confirmed the structural uniformity and consistent device performance across wafer-scale transistor arrays.

Conclusions:

• The developed passivation-driven epitaxy strategy is a breakthrough for scalable, single-orientation p-type TMD monolayers.
• This method provides a robust materials platform for advancing 2D electronics and optoelectronics.
• It effectively bridges the performance gap between n-type and p-type 2D semiconductors, paving the way for fully integrated 2D CMOS circuits.