TY - JOUR AU - Jiang, Shaolong AU - Yang, Jin AU - Shi, Yuping AU - Zhao, Jing AU - Xie, Chunyu AU - Zhao, Liyun AU - Fu, Jiatian AU - Yang, Pengfei AU - Huan, Yahuan AU - Xie, Qin AU - Jiang, Huachao AU - Zhang, Qing AU - Wang, Xianlong AU - Su, Fuhai AU - Zhang, Yanfeng PY - 2020 TI - Salt-assisted growth and ultrafast photocarrier dynamics of large-sized monolayer ReSe2 JO - Nano Research SN - 1998-0124 SP - 667 EP - 675 VL - 13 IS - 3 AB - Owing to its anisotropic optical and electrical properties, rhenium diselenide (ReSe2) has garnered considerable attention recently as a candidate material for polarization-sensitive photodetectors. However, the direct and controllable synthesis of large-sized ReSe2 with a uniform thickness is still a great challenge. Herein, we have refined the synthesis method to obtain uniform monolayer ReSe2 flakes with a size of up to ~ 106 μm on sapphire via an ambient-pressure chemical vapor deposition technique using Na promoter from sodium chloride. Interestingly, optical pump-probe spectroscopy revealed a fast switching from saturable absorption (SA) to absorption enhancement (AE) in subpicosecond time scale, followed by a slower decay induced by exciton recombination. Furthermore, both AE and SA signals exhibited clear angular dependence with a periodicity of 180°, which reflected the dichroism in nonlinear absorption dynamics. In addition, the photocarrier dynamics including free-carrier transport and subpicosecond relaxation due to exciton formation or surface trapping was probed using time resolved terahertz spectroscopy. We believe that our study serves as a reference for atomically controlled synthesis of large-sized ReSe2 and provides useful insights on its optoelectronic properties for novel device applications. UR - https://doi.org/10.1007/s12274-020-2673-4 DO - 10.1007/s12274-020-2673-4