@article{Jiang2020, author = {Shaolong Jiang and Jin Yang and Yuping Shi and Jing Zhao and Chunyu Xie and Liyun Zhao and Jiatian Fu and Pengfei Yang and Yahuan Huan and Qin Xie and Huachao Jiang and Qing Zhang and Xianlong Wang and Fuhai Su and Yanfeng Zhang}, title = {Salt-assisted growth and ultrafast photocarrier dynamics of large-sized monolayer ReSe2}, year = {2020}, journal = {Nano Research}, volume = {13}, number = {3}, pages = {667-675}, keywords = {chemical vapor deposition, ReSe2, sodium chloride, large size, ultrafast photocarrier dynamics}, url = {https://www.sciopen.com/article/10.1007/s12274-020-2673-4}, doi = {10.1007/s12274-020-2673-4}, abstract = {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.} }