Fabrication of Luminescent Monolayered Tungsten Dichalcogenides Quantum Dots with Giant Spin-Valley Coupling
Fabrication of Luminescent Monolayered Tungsten Dichalcogenides Quantum Dots with Giant Spin-Valley Coupling
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DOI：
10.1021/nn403682r
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发表时间：
2013-09-01
期刊：
影响因子：
17.1
通讯作者：
Allwood, Dan A.
中科院分区：
文献类型：
--
作者：
Lin, Liangxu;Xu, Yaoxian;Allwood, Dan A.
发展了一种高收率（> 36wt%）的从多层二硫属钨（WS 2）薄片制备横向尺寸接近8-15 nm的单层WS 2量子点（QD）的方法。单层WS 2 QD与单层WS 2片一样，是直接半导体，尽管薄片前体是间接半导体。然而，量子点有一个显着更大的直接跃迁能量（3.16 eV）相比，片（2.1 eV）和增强的光致发光（PL;量子产率类似于4%），在室温下的蓝绿色光谱区。UV/维斯测量揭示了一个巨大的自旋谷耦合的单层WS 2量子点在570 meV左右，这是大于单层WS 2片（类似于400 meV）。这种自旋-谷耦合被PL进一步证实为从导带最小值到分裂价带能级的直接跃迁，导致以369（3.36 eV）和461 nm（2.69 eV，也由新的缺陷能级贡献）为中心的多个发光峰。量子点的巨大自旋-谷耦合的发现和单层量子点的强发光使其在基于自旋电子学、概念谷电子学、量子信息技术和光电器件等方面具有潜在的应用价值。然而，我们也证明了所制造的单层WS 2量子点可以是高对比度生物成像应用的无毒荧光标记。
A high yield (>36 wt %) method has been developed of preparing monolayered tungsten dichalcogenide (WS2) quantum dots (QDs) with lateral size similar to 8-15 nm from multilayered WS2 flakes. The monolayered WS2 QDs are, like monolayered WS2 sheets, direct semiconductors despite the flake precursors being an indirect semiconductor. However, the QDs have a significantly larger direct transition energy (3.16 eV) compared to the sheets (2.1 eV) and enhanced photoluminescence (PL; quantum yield similar to 4%) in the blue-green spectral region at room temperature. UV/vis measurements reveal a giant spin-valley coupling of the monolayered WS2 QDs at around 570 meV, which is larger than that of monolayered WS2 sheets (similar to 400 meV). This spin-valley coupling was further confirmed by PL as direct transitions from the conduction band minimum to split valence band energy levels, leading to multiple luminescence peaks centered at around 369 (3.36 eV) and 461 nm (2.69 eV, also contributed by a new defect level). The discovery of giant spin-valley coupling and the strong luminescence of the monolayered WS2 QDs make them potentially of interests for the applications in semiconductor-based spintronics, conceptual valley-based electronics, quantum information technology and optoelectronic devices. However, we also demonstrate that the fabricated monolayered WS2 QDs can be a nontoxic fluorescent label for high contrast bioimaging application.