Pt-wedge squeegee cleaning of two-dimensional materials and heterostructures

TL;DR

This paper introduces a high-throughput AFM-based cleaning method for 2D materials using a Pt-wedge on the cantilever, significantly improving cleaning efficiency and sample quality.

Contribution

The study develops a modified AFM cleaning technique with a Pt-wedge, enabling rapid and scalable cleaning of 2D materials and heterostructures.

Findings

Achieved a cleaning rate of 3 μ^2/s with the modified AFM cantilever.

Enhanced photoluminescence of monolayer WS2 after cleaning.

Improved contact quality between WS2 and Au electrodes post-cleaning.

Abstract

The surface of ultra-thin 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 {\mu}^2/s can be achieved with our modified cantilevers, compared to the 0.01 {\mu}^2/s effective cleaning rate in pointy-tip cleaning. As showcases, we demonstrate that monolayer WS2 on h-BN exhibits much sharper photoluminescence (PL) emission at room temperature after AFM cleaning, and WS2 monolayers exhibit a higher quality contacts to cleaned Au electrodes as compared to uncleaned electrodes. We also showed 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.