Monolithic Integration of Crack‐Free 2D Bi 2 O 2 Se via Stress Modulation

ABSTRACT The monolithic integration of 2D materials into silicon‐based wafers is crucial for next‐generation electronics and optoelectronics. Reliable transfer methods for wafer‐scale 2D materials are a key prerequisite. As one of the most promising 2D semiconductors, bismuth oxygen selenide (Bi 2 O 2 Se) films show significant promise as high‐performance photodetectors and advanced‐architecture transistors. Although considerable efforts have been devoted to transfer methods for 2D Bi 2 O 2 Se, challenges such as limited film size, transfer‐induced defects, cracks, and contamination remain. Herein, we report a novel transfer method for wafer‐scale 2D Bi 2 O 2 Se single‐crystal films based on the stress modulation of metal films. A composite transfer medium comprising tensile‐stressed Ni and stress‐free Cu was developed to enable intact and crack‐free exfoliation of 2D Bi 2 O 2 Se films. By modulating the strain and fracture energies of the composite metal film, the transferred 4‐inch 2D Bi 2 O 2 Se film exhibited a crack‐free, intact, and uniform morphology, and two‐layer and three‐layer‐stacked 2D Bi 2 O 2 Se films with clean interfaces were fabricated. Integrated 2D Bi 2 O 2 Se transistors exhibit high carrier mobility reaching up to ∼150 cm 2 V −1 s −1 with an on/off ratio ∼10 6 , which is better than other transferred wafer‐scale 2D semiconductors. Overall, our findings are promising for the future integration of 2D materials into advanced electronics and optoelectronics.