Nanoscale Cathodoluminescence and Conductive Mode Scanning Electron Microscopy of van der Waals Heterostructures.
Nanoscale Cathodoluminescence and Conductive Mode Scanning Electron Microscopy of van der Waals Heterostructures.
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DOI：
10.1021/acsnano.3c03261
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发表时间：
2023-06-27
期刊：
影响因子：
17.1
通讯作者：
Chhowalla, Manish
中科院分区：
文献类型：
--
作者：
Ramsden, Hugh;Sarkar, Soumya;Wang, Yan;Zhu, Yiru;Kerfoot, James;Alexeev, Evgeny M.;Taniguchi, Takashi;Watanabe, Kenji;Tongay, Sefaattin;Ferrari, Andrea C.;Chhowalla, Manish
关键词：
Van der Waals异质结构（VDW-HSS）整合了不同的材料以形成复杂的设备。这些取决于在多个接口处对电荷的操纵。但是，目前，在设备中可能未发现应变，掺杂或电气断裂的亚微米变化，从而不利地影响了宏观的性能。在这里，我们使用导电模式和阴极发光扫描电子显微镜（CM-SEM和SEM-CL）来研究这些现象。作为模型系统，我们使用固定硼化硼（HBN）中封装的单层WSE2（1L-WSE2）。 CM-SEM允许在SEM测量过程中定量电子流。在5 keV的电子辐照过程中，高达70％的梁电子被沉积到VDW-HS中，随后可以迁移到1L-WES2。电荷的积累导致1L-WE2的动态掺杂，在30 s上降低了30％的CL效率。通过提供多余电子离开样品的路径，可以实现对初始CL信号的完全恢复。这些结果表明，必须考虑在电子辐照过程中捕获电荷在电子辐照过程中的捕获，以便在EBEAM光刻或SEM等过程中获得和维持VDW-HS设备的最佳性能。因此，CM-SEM和SEM-CL形成了一种工具包，可以通过该工具包进行VDW-HS设备的纳米级表征，从而可以将电气和光学性质相关。
van der Waals heterostructures (vdW-HSs) integrate dissimilar materials to form complex devices. These rely on the manipulation of charges at multiple interfaces. However, at present, submicrometer variations in strain, doping, or electrical breakages may exist undetected within a device, adversely affecting macroscale performance. Here, we use conductive mode and cathodoluminescence scanning electron microscopy (CM-SEM and SEM-CL) to investigate these phenomena. As a model system, we use a monolayer WSe2 (1L-WSe2) encapsulated in hexagonal boron nitride (hBN). CM-SEM allows for quantification of the flow of electrons during the SEM measurements. During electron irradiation at 5 keV, up to 70% of beam electrons are deposited into the vdW-HS and can subsequently migrate to the 1L-WSe2. This accumulation of charge leads to dynamic doping of 1L-WSe2, reducing its CL efficiency by up to 30% over 30 s. By providing a path for excess electrons to leave the sample, near full restoration of the initial CL signal can be achieved. These results indicate that the trapping of charges in vdW-HSs during electron irradiation must be considered, in order to obtain and maintain optimal performance of vdW-HS devices during processes such as e-beam lithography or SEM. Thus, CM-SEM and SEM-CL form a toolkit through which nanoscale characterization of vdW-HS devices can be performed, allowing electrical and optical properties to be correlated.
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