Data for main text figures - In situ engineering hexagonal boron nitride in van der Waals heterostructures with selective SF6 etching

Data includes AFM, Raman, and Transport measurements of graphene heterostructures before and after etching with SF6. Abstract: Van der Waals heterostructures are at the forefront in materials heterostructure engineering, offering the ultimate control in layer selectivity and capability to combine virtually any material. Hexagonal-boron nitride, the most commonly used dielectric material, has proven indispensable in this field, allowing the encapsulation of active 2D materials preserving their exceptional electronic quality. However, not all device applications require full encapsulation but rather require open surfaces, or even selective patterning of hBN layers. Here, we report on a procedure to engineer top hBN layers within van der Waals heterostructures while preserving the underlying active 2D layers. Using a soft selective SF6 etching combined with a series of pre and post-etching treatments, we demonstrate that pristine surfaces can be exposed with atomic flatness while preserving the active layers’ electronic quality. We benchmark our technique using graphene/hBN Hall bar devices. Using Raman spectroscopy combined with quantum transport, we show high quality can be preserved in etched regions by demonstrating low temperature carrier mobilities > 200,000 cm2/Vs, ballistic transport probed through magnetic focusing, and intrinsic room temperature phonon-limited mobilities. Atomic force microscopy brooming and O2 plasma cleaning are identified as key pre-etching steps to obtaining pristine open surfaces while preserving electronic quality. The technique provides a clean method for opening windows into mesoscopic van der Waals devices that can be used for local probe experiments, patterning top hBN in-situ, and exposing 2D layers to their environment for sensing applications.本数据集包含六氟化硫（SF6）刻蚀前后石墨烯异质结的原子力显微镜（Atomic Force Microscope, AFM）、拉曼光谱（Raman spectroscopy）及输运测量数据。 摘要：范德瓦尔斯异质结（Van der Waals heterostructures）是材料异质结工程的前沿方向，可实现层选择性的极致调控，并几乎可组合任意种类的材料。六方氮化硼（hexagonal-boron nitride, hBN）作为当前最常用的介电材料，已被证实为该领域不可或缺的核心材料，可实现有源二维材料的封装并保留其优异的电子性能。然而，并非所有器件应用都需要全封装结构，部分场景仅需开放表面，甚至需要对六方氮化硼层进行选择性图案化。本研究报道了一种可在范德瓦尔斯异质结中加工顶层六方氮化硼层，同时完整保留下层有源二维材料的工艺方法。通过结合软选择性六氟化硫刻蚀与一系列刻前、刻后处理工艺，研究证实可暴露出原子级平整的纯净表面，同时保留有源层的电子性能。本研究以石墨烯/六方氮化硼霍尔棒器件（Hall bar devices）为基准对该工艺进行性能验证，结合拉曼光谱与量子输运（quantum transport）测量，通过以下结果证实刻蚀区域可保持优异品质：低温载流子迁移率超过200,000 cm²/(V·s)、通过磁聚焦（magnetic focusing）效应探测到弹道输运（ballistic transport），以及本征室温声子限制迁移率。研究发现，原子力显微镜扫拭工艺与氧气等离子体（O2 plasma）清洁工艺是获取纯净开放表面、同时保留电子性能的关键刻前步骤。该工艺为介观范德瓦尔斯器件开辟窗口提供了一种洁净的技术方案，可应用于局域探针实验、原位图案化顶层六方氮化硼，以及将二维材料暴露于环境中以用于传感应用。