Valley phenomena in the candidate phase change material WSe2(1-x)Te2x
Valley phenomena in the candidate phase change material WSe2(1-x)Te2x
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候选相变材料WSe2(1-x)Te2x中的谷现象
DOI：
10.1038/s42005-019-0277-7
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发表时间：
2020-01-15
影响因子：
5.5
通讯作者：
Vora, Patrick M.
中科院分区：
文献类型：
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作者：
Oliver, Sean M.;Young, Joshua;Vora, Patrick M.
合金化的过渡金属二卤化物提供了一条通往原子薄相变存储器的途径，这种存储器承载着山谷电子行为。在这里，拉曼光谱和光致发光光谱被用来证明单层合金中的谷极化对化学取代的稳健性。合金过渡金属双卤化物提供了在原子薄的平台上耦合带工程和谷电子现象的机会。然而，合金中的山谷性质在很大程度上仍未被开发。我们研究了相变候选材料WSe_2(1-x)Te_2x单层合金中的谷自由度。低温拉曼测量跟踪了合金诱导的从WSe2的半导体1H相到WTe2的半金属1T(D)相的转变。我们将这些观测结果与密度泛函理论计算相关联，并从1H相合金的W-Te振动中识别出新的拉曼模式。光致发光测量显示了超低能量发射特征，突出了由于较大的W-Te键长而引起的合金无序。有趣的是，合金中的谷极化和相干性在高Te组分下仍然存在，并且比在WSe2中更能抵抗温度的影响。这些发现说明了具有高度不同母体化合物的合金中谷性质的持久性，并表明可以利用能带工程来制造阀门电子器件。
Alloyed transition metal dichalcogenides provide a route toward atomically-thin phase change memories that host valleytronic behaviours. Here, Raman and photoluminescence spectroscopies are employed to demonstrate the robustness of valley polarisation to chemical substitution in monolayer alloys.Alloyed transition metal dichalcogenides provide an opportunity for coupling band engineering with valleytronic phenomena in an atomically-thin platform. However, valley properties in alloys remain largely unexplored. We investigate the valley degree of freedom in monolayer alloys of the phase change candidate material WSe2(1-x)Te2x. Low temperature Raman measurements track the alloy-induced transition from the semiconducting 1H phase of WSe2 to the semimetallic 1T(d) phase of WTe2. We correlate these observations with density functional theory calculations and identify new Raman modes from W-Te vibrations in the 1H-phase alloy. Photoluminescence measurements show ultra-low energy emission features that highlight alloy disorder arising from the large W-Te bond lengths. Interestingly, valley polarization and coherence in alloys survive at high Te compositions and are more robust against temperature than in WSe2. These findings illustrate the persistence of valley properties in alloys with highly dissimilar parent compounds and suggest band engineering can be utilized for valleytronic devices.