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Optical Properties and Photocarrier Dynamics of Bi2O2Se Monolayer and Nanoplates
Advanced Optical Materials ( IF 8.0 ) Pub Date : 2020-01-10 , DOI: 10.1002/adom.201901567 Shuangyan Liu 1 , Congwei Tan 2 , Dawei He 1 , Yongsheng Wang 1 , Hailin Peng 2 , Hui Zhao 3
Advanced Optical Materials ( IF 8.0 ) Pub Date : 2020-01-10 , DOI: 10.1002/adom.201901567 Shuangyan Liu 1 , Congwei Tan 2 , Dawei He 1 , Yongsheng Wang 1 , Hailin Peng 2 , Hui Zhao 3
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A comprehensive experimental study on optical properties and photocarrier dynamics in Bi2O2Se monolayers and nanoplates is presented. Large and uniform Bi2O2Se nanoplates with various thicknesses down to the monolayer limit are fabricated. In nanoplates, a direct optical transition near 720 nm is identified by optical transmission, photoluminescence, and transient absorption spectroscopic measurements and is attributed to the transition between the valence and conduction bands in the Γ valley. Time‐resolved differential reflection measurements reveal ultrafast carrier thermalization and energy relaxation processes and a photocarrier recombination lifetime of about 200 ps in nanoplates. Furthermore, by spatially resolving the differential reflection signal, a photocarrier diffusion coefficient of about 4.8 cm2 s−1 is obtained, corresponding to a mobility of about 180 cm2 V−1 s−1. A similar direct transition is also observed in monolayer Bi2O2Se, suggesting that the states in the Γ valley do not change significantly with the thickness. The temporal dynamics of the excitons in the monolayer is quite different from the nanoplates, with a strong saturation effect and fast exciton–exciton annihilation at high densities. Spatially and temporally resolved measurements yield an exciton diffusion coefficient of about 20 cm2 s−1.
中文翻译：
Bi2O2Se单层和纳米板的光学性质和光载流子动力学
提出了Bi 2 O 2 Se单层和纳米板中光学性质和光载流子动力学的综合实验研究。大而均匀的Bi 2 O 2制备了具有低至单层极限的各种厚度的Se纳米板。在纳米板中，通过光学透射，光致发光和瞬态吸收光谱测量可以识别出接近720 nm的直接光学跃迁，这归因于Γ谷的价带和导带之间的跃迁。时间分辨的差分反射测量揭示了纳米板上超快的载流子热化和能量弛豫过程，以及光载流子复合寿命约为200 ps。此外，通过在空间上分辨差分反射信号，获得约4.8 cm 2 s -1的光载流子扩散系数，对应于约180 cm 2 V -1 s的迁移率。-1。在单层Bi 2 O 2 Se中也观察到类似的直接跃迁，这表明Γ谷中的状态不会随厚度而显着变化。单分子层中激子的时间动态与纳米板完全不同，在高密度下具有很强的饱和效应和快速的激子-激子an灭。时空分辨的测量结果得出激子扩散系数约为20 cm 2 s -1。
更新日期：2020-03-20
中文翻译：
Bi2O2Se单层和纳米板的光学性质和光载流子动力学
提出了Bi 2 O 2 Se单层和纳米板中光学性质和光载流子动力学的综合实验研究。大而均匀的Bi 2 O 2制备了具有低至单层极限的各种厚度的Se纳米板。在纳米板中，通过光学透射，光致发光和瞬态吸收光谱测量可以识别出接近720 nm的直接光学跃迁，这归因于Γ谷的价带和导带之间的跃迁。时间分辨的差分反射测量揭示了纳米板上超快的载流子热化和能量弛豫过程，以及光载流子复合寿命约为200 ps。此外，通过在空间上分辨差分反射信号，获得约4.8 cm 2 s -1的光载流子扩散系数，对应于约180 cm 2 V -1 s的迁移率。-1。在单层Bi 2 O 2 Se中也观察到类似的直接跃迁，这表明Γ谷中的状态不会随厚度而显着变化。单分子层中激子的时间动态与纳米板完全不同，在高密度下具有很强的饱和效应和快速的激子-激子an灭。时空分辨的测量结果得出激子扩散系数约为20 cm 2 s -1。
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