Second-harmonic generation divergence-a method for domain size evaluation of 2D materials.

Single-atomic-layered materials are important for future electronics. They allow optoelectronic devices to be fabricated at the single-atomic layer level. A single-atomic-layered two-dimensional (2D) transition metal dichalcogenide (TMD) film is usually composed of randomly orientated single-crystalline domains, and the size distribution of the domains on a large-area film has a significant impact on the applications of the film, but the impact is difficult to characterize. We report an approach to evaluate the size of the single-crystalline domains by measuring the second-harmonic generation divergence caused by the domains of different orientations. Using this method, domain size mapping on an 8×8 region of a continuous film is achieved. This method provides a fast and efficient way of domain size characterization across a large area in a non-destructive and transfer-free manner for single-atomic-layered TMD films.