School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China.
Nanoscale. 2017 Aug 10;9(31):11027-11034. doi: 10.1039/c7nr02025b.
Two-dimensional transition metal dichalcogenides (TMDCs) exhibit excellent optoelectronic properties. However, the large band gaps in many semiconducting TMDCs make optical absorption in the near-infrared (NIR) wavelength regime impossible, which prevents applications of these materials in optical communications. In this work, we demonstrate that Ar ion irradiation is a powerful post-synthesis technique to tailor the optical properties of the semiconducting tungsten disulfide (WS) by creating S-vacancies and thus controlling material stoichiometry. First-principles calculations reveal that the S-vacancies give rise to deep states in the band gap, which determine the NIR optical absorption of the WS monolayer. As the density of the S-vacancies increases, the enhanced NIR linear and saturable absorption of WS is observed, which is explained by the results of first-principles calculations. We further demonstrate that by using the irradiated WS as a saturable absorber in a waveguide system, the passively Q-switched laser operations can be optimized, thus opening new avenues for tailoring the optical response of TMDCs by defect-engineering through ion irradiation.
二维过渡金属二硫属化物 (TMDCs) 表现出优异的光电性能。然而，许多半导体 TMDCs 的大带隙使得在近红外 (NIR) 波长范围内的光学吸收成为不可能，这阻碍了这些材料在光通信中的应用。在这项工作中，我们证明了 Ar 离子辐照是一种通过创建 S 空位从而控制材料化学计量来调整半导体二硫化钨 (WS) 光学性质的强大后合成技术。第一性原理计算表明，S 空位在带隙中产生深能级，决定了 WS 单层的近红外光吸收。随着 S 空位密度的增加，观察到 WS 的增强的近红外线性和饱和吸收，这可以通过第一性原理计算的结果来解释。我们进一步证明，通过在波导系统中使用辐照 WS 作为可饱和吸收体，可以优化被动调 Q 激光操作，从而通过离子辐照的缺陷工程为调整 TMDCs 的光学响应开辟新途径。
