Highly crystalline ReSe2 atomic layers synthesized by chemical vapor transport

Two-dimensional (2D) anisotropic rhenium diselenide (ReSe2) has attracted lots of attention due to its promising applications in electronics and optoelectronics. However, controlled synthesis of high quality ultrathin ReSe2 remains as a challenge. Here we developed an approach for synthesizing high quality 2D ReSe2 flakes with a thickness down to monolayer by chemical vapor transport (CVT) through carefully tuning the growth kinetics. The atomic structures and anisotropy of the obtained ReSe2 flakes were intensively characterized with scanning transmission electron microscope and angle-resolved polarized Raman spectroscopy. Field-effect transistors fabricated on the CVT-grown ReSe2 flakes showed n-type semiconducting behavior with an on/off current ratio of 10(5) and a mobility up to similar to 5 cm(2) V-1 s(-1), which is comparable to mechanically exfoliated flakes and is obvious higher than the samples synthesized with other approaches. This study not only make high quality 2D ReSe2 easily accessible for both fundamental and application explorations but also sheds new lights on the chemical synthesis of other anisotropic 2D materials.