Stacking Orientation-Dependent Photoluminescence Pathways in Artificially Stacked Bilayer WS2 Nanosheets Grown by Chemical Vapor Deposition: Implications for Spintronics and Valleytronics
Stacking Orientation-Dependent Photoluminescence Pathways in Artificially Stacked Bilayer WS2 Nanosheets Grown by Chemical Vapor Deposition: Implications for Spintronics and Valleytronics
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DOI：
10.1021/acsanm.1c00192
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发表时间：
2021-03-28
影响因子：
5.9
通讯作者：
Ago, Hiroki
中科院分区：
文献类型：
--
作者：
Ji, Hyun Goo;Solis-Fernandez, Pablo;Ago, Hiroki
具有直接光学带隙的过渡金属二硫属化物（TMD）纳米片单层膜由于其优异的光学性质和在自旋电子学和谷电子学中的潜在应用而引起了极大的关注。最近，层状材料的堆叠配置已被证明提供了额外的自由度来控制它们的物理性质。通过控制其堆叠取向，在TMD的均质双层中观察到独特的物理性质，例如层间激子和超导性。在这里，我们使用人工堆叠的化学气相沉积（CVD）生长的二硫化钨（WS2）制造具有各种堆叠角度的同质双层。人工叠层的光致发光（PL）光谱随叠层角呈60度周期性变化。一个额外的低能量PL峰被观察到的低角度堆叠的双层，这是由电光测量揭示起源于间接层内激子弛豫。此外，我们发现，我们的CVD生长的WS2的高光学质量是一个关键因素，在观察本征激子动力学的缺陷诱导的局域激子。我们的工作揭示了通过调节高质量单层的堆叠来控制TMD均质双层的光学性质的调制。
Having a direct optical band gap, monolayers of transition metal dichalcogenide (TMD) nanosheets have attracted great attention due to their exceptional optical properties and potential applications in spintronics and valleytronics. Recently, the stacking configuration of layered materials has been proved to offer an additional degree of freedom to control their physical properties. Unique physical properties, such as interlayer excitons and superconductivity, have been observed in homobilayers of TMDs by controlling their stacking orientation. Here, we use artificial stackings of chemical vapor deposition (CVD)-grown tungsten disulfide (WS2) to fabricate homobilayers with various stacking angles. The artificial stacks showed a 60 degrees periodic change of their photoluminescence (PL) spectra with the stacking angle. An additional low-energy PL peak was observed for the low-angle stacked bilayers, which was revealed by electro-optical measurements to originate in the indirect intralayer exciton relaxation. In addition, we found the high optical quality of our CVD-grown WS2 to be a key factor in observing the intrinsic exciton dynamics free from defect-induced localized excitons. Our work sheds light on the controlled modulation of the optical properties of TMD homobilayers by tuning the stacking of high-quality monolayers.