Strain effect on electronic and transport properties of WSe2 monolayers with grain boundaries: First-principles insights.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have emerged as promising materials for functional electronic devices owing to their outstanding mechanical, electronic, and optoelectronic properties. However, it remains a challenge to experimentally synthesize large-scale defect-free crystalline structures. The defects, such as grain boundaries, often exist and play an important role in determining their physical and chemical properties. In this work, by means of first-principles calculations, the effects of a typical grain boundary (composed of 5-7 membered rings) and uniaxial strains on electronic and transport properties of WSe2 monolayers are systematically investigated. It is observed that the local atomic arrangements, particularly the inter-grain spacing and elastic strains, significantly affect electronic and transport properties. The underlying mechanism is carefully elucidated. Furthermore, the flexoelectricity enhanced piezoelectric properties of WSe2 monolayers with grain boundaries are clarified. Our findings demonstrate that grain boundary engineering and strain modulation offer a versatile approach to tailoring the electronic and transport properties of 2D TMDs.