Large area thin exfoliation of van der Waals magnetic and topological crystals and pickup using a Au-assisted method

The exfoliation of large area, thin flakes from van der Waals (vdW) crystals remains a challenge for advancing their integration into functional devices. Conventional tape-based mechanical exfoliation often produces small flakes with limited reproducibility, limiting their utility for large-scale heterostructure assembly. In this talk, I will demonstrate a gold assisted exfoliation method for producing large-area, thin flakes of diverse vdW crystals, including graphene, topological semimetals, and magnetic crystals. Flakes produced by this method have been successfully integrated into vdW devices characterized using spin-polarized low-energy electron microscopy (SPLEEM) at the Molecular Foundry, Lawrence Berkeley National Laboratory, demonstrating the suitability of Au-assisted exfoliation for surface-sensitive measurements and device fabrication.

For the topological Dirac semimetal PtTe₂, this method yields large-area flakes with uniform surfaces and thicknesses of about 10 nm, confirmed by atomic force microscopy. We further explore key parameters in the exfoliation process that control flake thickness and area across different material classes.

Overall, our use of Au assisted exfoliation demonstrates two major achievements: production and pickup of monolayer graphene flakes at large scales for device integration, and exfoliation of novel vdW materials of similar scale suitable for large scale surface sensitive microscopy and spectroscopy.