Vertically oriented few-layered HfS 2 nanosheets: growth mechanism and optical properties

For the first time, large-area, vertically oriented few-layered hafnium disulfide (V- ) nanosheets have been grown by chemical vapor deposition. The individual nanosheets are well [001] oriented, with highly crystalline quality. Far different from conventional van der Waals epitaxial growth mechanism for two-dimensional transition metal dichalcogenides, a novel dangling-bond-assisted self-seeding growth mechanism is proposed to describe the growth of V- nanosheets: difficult migration of adatoms on substrate surface results in seeds growing perpendicularly to the substrate; V- nanosheets inherit the growth direction of seeds; V- nanosheets further expand in the in-plane direction with time evolution. Moreover, the V- nanosheets show strong and broadened photons absorption from near infrared to ultraviolet; the V- -based photodetector exhibits an ultrafast photoresponse time of 24 ms, and a high photosensitivity ca. 10 3 for 405 nm laser.