Visualizing Heteroepitaxy of Angle-Oriented GeSe/WSe₂ Heterostructures for Near-Infrared Ultrasensitive Photodetectors

Here, we demonstrate a visualized and directed heteroepitaxy strategy for GeSe on WSe₂ by integrating in situ imaging with symmetry-guided physical vapor deposition. Real-time observation captures the nucleation kinetics and orientation evolution, accelerating process optimization.

Combined density functional theory calculations and transmission electron microscope characterizations identify a preferential epitaxial angle of 20° (occurrence: 59.37%) for most GeSe nanosheets, corresponding to the global energy minimum governed by lattice symmetry. Coverage-tunable photodetectors are constructed by modulating GeSe nanosheets’ number, delivering a three-orders-of-magnitude enhancement in responsivity at 808 nm (823.8 A/W at maximum coverage).