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Ultrafast Relaxation Dynamics and Nonlinear Response of Few‐Layer Niobium Carbide MXene
Small Methods ( IF 12.4 ) Pub Date : 2020-05-11 , DOI: 10.1002/smtd.202000250
Lingfeng Gao 1 , Hualong Chen 1 , Feng Zhang 1 , Shan Mei 2 , Ye Zhang 1 , Wenli Bao 1 , Chunyang Ma 1 , Peng Yin 1 , Jia Guo 1 , Xiantao Jiang 1 , Shixiang Xu 3 , Weichun Huang 4 , Xiaobo Feng 5 , Fuming Xu 3 , Songrui Wei 1 , Han Zhang 1
Affiliation  

As one of the rising 2D materials, niobium‐carbide (Nb2C, well‐known as a member of MXene family) has attracted considerable attention owing to its unique physical and chemical properties. In this work, few‐layer Nb2C nanosheets (NSs) with large (≈255 nm) and small (≈48 nm) lateral dimensions are obtained via a combination of selective etching and liquid cascade centrifugation. Their relaxation time and photophysics process are systematically investigated by transient absorption spectroscopy, and the size effect is demonstrated by phonon‐bottleneck mechanism. Ultrafast fast relaxation time (37.43 fs) and slow relaxation time (0.5733 ps) are observed due to the symmetric structure and metallicity of Nb2C NSs. The nonlinear optical properties of Nb2C NSs are studied by Z‐scan technique, and both saturable absorption and reverse‐saturable absorption are observed. According to first principle calculations, these phenomena can be attributed to the special band structure of Nb2C near the Fermi level, where two‐photon absorption or multiphoton absorption may occur under the irradiation of long wavelength light. These intriguing results suggest that few‐layer Nb2C NSs can be used as building blocks for broadband ultrafast photonics and optoelectronic devices and also hold the potential for breakthrough developments in these fields.

中文翻译:

几层碳化铌MXene的超快弛豫动力学和非线性响应

作为新兴的2D材料之一,碳化铌(Nb 2 C,众所周知为MXene系列的一员)由于其独特的物理和化学特性而受到了广泛的关注。在这项工作中,通过选择性刻蚀和液体级联离心相结合,获得了具有大尺寸(≈255nm)和小尺寸(≈48nm)的几层Nb 2 C纳米片(NSs)。通过瞬态吸收光谱系统地研究了它们的弛豫时间和光物理过程,并通过声子-瓶颈机制证明了其尺寸效应。由于Nb 2 C NSs的对称结构和金属性,观察到超快的快速弛豫时间(37.43 fs)和缓慢的弛豫时间(0.5733 ps)。Nb的非线性光学性质通过Z扫描技术研究了2 C NSs,同时观察到了饱和吸收和反向饱和吸收。根据第一原理计算,这些现象可归因于费米能级附近的Nb 2 C的特殊能带结构,在长波长光的照射下,可能发生双光子吸收或多光子吸收。这些有趣的结果表明,很少层的Nb 2 C NS可以用作宽带超快光子学和光电设备的基础,并且在这些领域具有突破性发展的潜力。
更新日期:2020-05-11
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