Controlled Synthesis of Twisted Bilayer WSe2 Via Hydrogen Pulse and Water-Assisted CVD

Abstract

Twisted bilayer tungsten diselenide (TB-WSe2), which combines twist-angle-dependent electronic band structure with broken inversion symmetry, is particularly attractive for ultrathin optoelectronic and ferroelectric devices. However, TB-WSe2 is still synthesized by mechanical exfoliation and artificial stacking, which suffer from low yield, interfacial contamination, and lattice damage. In this work, we develop a chemical vapor deposition strategy that integrates water-assisted precursor engineering with hydrogen-pulse modulation to enable the controlled synthesis of TB-WSe2. Temperature-dependent PL measurements reveal an additional interlayer-exciton emission in TB-WSe2 compared with the conventionally stacked AA bilayer and, further, reveal the temperature evolution of the PL peak positions and intensities. Piezoresponse force microscopy confirms out-of-plane polarization at selected twist angles, as evidenced by representative butterfly-shaped amplitude loops and phase-switching hysteresis curves. This work establishes a high-yield synthesis route for TB-WSe2 and provides an experimental foundation for the development and practical application of two-dimensional twisted transition-metal dichalcogenide-based optoelectronic and ferroelectric devices.