Robust enhancement of valley polarization and quantum yield in composition grading lateral heterostructure of MoS2-WS2 monolayer

IF 4.8 2区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Progress in Natural Science: Materials International Pub Date : 2024-02-01 DOI:10.1016/j.pnsc.2024.02.014

Mengke Kang , Cheng Zhang , Congpu Mu , Kun Zhai , Tianyu Xue , Bochong Wang , Fusheng Wen , Yingchun Cheng , Jianyong Xiang , Jun-Feng Dai , Anmin Nie , Zhongyuan Liu

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Abstract

Valley degeneracy can be broken owing to the strong spin-orbit coupling in two-dimensional transition metal dichalcogenides (2D-TMDCs). Valley-dependent interaction of carriers in TMDCs with different circular polarizations of light offers valley degree-of-freedom besides charge and spin to carry information. Thus, bandgap engineering of 2D-TMDCs plays a critical role in developing practical valleytronic devices. Hereby, we demonstrate a great enhancement in quantum yield as well as polarization of monolayer MoS₂ achieved by gradually alloying W atoms in MoS₂. By appropriately setting a time offset between the evaporation of MoO₃ and WO₃ precursors during chemical vapor deposition, a compositionally graded heterostructure of MoS₂-WS₂ monolayer can be readily grown at large scale. Raman and transmission electron microscopy measurements demonstrate that the interface possesses a steep gradient in composition, spanning from MoS₂ to WS₂ over a length ∼2 μm. Compared to pure monolayer MoS₂, the photoluminescence intensity at the compositionally graded interface of Mo_1-xW_xS₂ was observed to increase by a factor of 16 owing to the effective separation of photogenerated carriers by the built-in electric field. Particularly, a remarkably high polarization of 70% at 16 K is demonstrated for the compositionally graded interface of Mo_1-xW_xS₂, which is ∼1.4 times larger than that in MoS₂ and is attributed to the combined effect of the alloyed structure and graded bandgap. Such an engineering scheme with a graded bandgap offers new approach for the development of high-efficiency valleytronics devices.

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在 MoS2-WS2 单层的成分分级横向异质结构中，谷极化和量子产率的稳健增强

由于二维过渡金属二钙化物（2D-TMDCs）中的强自旋轨道耦合，谷变性可以被打破。二维过渡金属二掺杂化合物中的载流子与不同圆偏振光之间的沟谷相互作用提供了除电荷和自旋之外的沟谷自由度，从而携带信息。因此，2D-TMDCs 的带隙工程在开发实用的谷电子器件中起着至关重要的作用。在此，我们展示了通过在 MoS 中逐渐合金化 W 原子，单层 MoS 的量子产率和偏振性都得到了极大的提高。在化学气相沉积过程中，通过适当设置氧化钼和 WO 前驱体蒸发之间的时间偏移，可以很容易地大规模生长出单层 MoS-WS 的成分分级异质结构。拉曼和透射电子显微镜测量结果表明，界面具有陡峭的成分梯度，从 MoS 到 WS 的跨度为 2 μm。与纯单层 MoS 相比，由于内置电场有效地分离了光生载流子，在 MoWS 成分梯度界面上观察到的光致发光强度增加了 16 倍。特别是在 16 K 时，MoWS 成分分级界面的极化率高达 70%，是 MoS 的 1.4 倍，这归功于合金结构和分级带隙的共同作用。这种具有梯度带隙的工程方案为开发高效谷电器件提供了新方法。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Progress in Natural Science: Materials International 综合性期刊-综合性期刊

CiteScore

8.60

自引率

2.10%

发文量

2812

审稿时长

49 days

期刊介绍： Progress in Natural Science: Materials International provides scientists and engineers throughout the world with a central vehicle for the exchange and dissemination of basic theoretical studies and applied research of advanced materials. The emphasis is placed on original research, both analytical and experimental, which is of permanent interest to engineers and scientists, covering all aspects of new materials and technologies, such as, energy and environmental materials; advanced structural materials; advanced transportation materials, functional and electronic materials; nano-scale and amorphous materials; health and biological materials; materials modeling and simulation; materials characterization; and so on. The latest research achievements and innovative papers in basic theoretical studies and applied research of material science will be carefully selected and promptly reported. Thus, the aim of this Journal is to serve the global materials science and technology community with the latest research findings. As a service to readers, an international bibliography of recent publications in advanced materials is published bimonthly.