Controllable synthesis of band-gap-tunable and monolayer transition-metal dichalcogenide alloys
Controllable synthesis of band-gap-tunable and monolayer transition-metal dichalcogenide alloys
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DOI：
10.3389/fenrg.2014.00027
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发表时间：
2014-01-01
影响因子：
3.4
通讯作者：
Li, Lain-Jong
中科院分区：
文献类型：
--
作者：
Su, Sheng-Han;Hsu, Wei-Ting;Li, Lain-Jong
过渡金属二硫属化物（TMD）材料的能隙直接决定了其电学和光学性质，因此，带隙工程已成为近年来的一个重要课题。理论和一些实验结果表明，这些monolayerTMD合金表现出直接带隙的性质，并保持稳定，在室温下，使他们有吸引力的光电应用。在这里，我们系统地比较了两种形成MoS_2xSe_2（1_x）单层合金的方法：MoS_2的硒化和MoSe_2的硫化。化学气相沉积MoS 2的光学能隙可以通过反应温度从1.86 eV（667 nm）连续调制到1.57 eV（790 nm）。光谱和显微观察表明，Mo-S键可以被MoSe键随机均匀地取代。相比之下，Mo-S取代MoSe不是随机发生在MoSe 2晶格中，其中反应优先沿着MoSe 2的晶体取向发生，因此在合金中容易观察到MoSe 2/MoS 2双相，这使得这些合金的光学带隙明显不同。因此，硒化的金属二硫化物是优选的，所提出的合成策略开辟了一个简单的路线来控制原子结构以及单层TMD合金的光学性能。
The electronic and optical properties of transition-metal dichalcogenide (TMD) materials are directly governed by their energy gap; thus, band-gap engineering has become an important topic recently. Theoretical and some experimental results have indicated that these monolayerTMD alloys exhibit direct-gap properties and remain stable at room temperature, making them attractive for optoelectronic applications. Here, we systematically compared the two approaches of forming MoS2xSe2(1_x) monolayer alloys: selenization of MoS2 and sulfurization of MoSe2. The optical energy gap of as-grown chemical vapor deposition MoS2 can be continuously modulated from 1.86 eV (667 nm) to 1.57 eV (790 nm) controllable by the reaction temperature. Spectroscopic and microscopic evidences show that the Mo-S bonds can be replaced by the Mo Se bonds in a random and homogeneous manner. By contrast, the replacement of Mo Se by Mo-S does not randomly occur in the MoSe2 lattice, where the reaction preferentially occurs along the crystalline orientation of MoSe2 and thus the MoSe2/MoS2 biphases are easily observed in the alloys, which makes the optical band gap of these alloys distinctly different. Therefore, the selenization of metal disulfide is preferred and the proposed synthetic strategy opens up a simple route to control the atomic structure as well as optical properties of monolayer TMD alloys.