Pt-Wedge Squeegee Cleaning of Two-Dimensional Materials and Heterostructures

High Resolution Image Download MS PowerPoint Slide The surface of ultrathin materials plays a crucial role in determining the properties. This is particularly important in two-dimensional (2D) materials where the surface-bulk distinction is no longer present. While mechanical cleaning of two-dimensional materials to remove interfacial and surface contaminants is used to achieve better sample quality, low throughput and the challenging optimization of cleaning procedures hinder their widespread adoption. Here, we report on atomic force microscope (AFM)-based mechanical cleaning with modified AFM cantilevers for high-throughput and easy-to-implement cleaning of 2D materials and their heterostructures. A Pt-wedge is deposited via focused ion beam on the cantilever to improve the mechanical cleaning of samples and streamline the cleaning procedures. We demonstrate that a cleaning rate of 3 μm 2 /s can be achieved with our modified cantilevers, compared to the 0.01 μm 2 /s effective cleaning rate in pointy-tip cleaning. As showcases, we demonstrate that monolayer WS 2 on h-BN exhibits much sharper photoluminescence (PL) emission at room temperature after AFM cleaning, and WS 2 monolayers exhibit higher-quality contacts to cleaned Au electrodes as compared to uncleaned electrodes. We also show that h-BN encapsulated heterostructures can be cleaned rapidly using the improved method. Overall, our results exhibit a feasible and facile path for the large-scale application of AFM-based cleaning of integrated 2D materials.