Highly crystalline ReSe₂ atomic layers synthesized by chemical vapor transport

Abstract 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 10⁵ and a mobility up to ∼5 cm² 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.