Dry pick-and-flip assembly of van der Waals heterostructures for microfocus angle-resolved photoemission spectroscopy

Abstract

We present a dry pick-and-flip assembly technique for angle-resolved photoemission spectroscopy (ARPES) of van der Waals heterostructures. By combining Elvacite2552C acrylic resin and 1-ethyl-3-methylimidazolium ionic liquid, we prepared polymers with glass transition temperatures (T_g) ranging from 37 to 100 ℃. The adhesion of the polymer to the 2D crystals was enhanced at [Formula: see text]. By utilizing the difference in [Formula: see text], a 2D heterostructure can be transferred from a high-[Formula: see text] polymer to a lower-[Formula: see text] polymer, which enables flipping its surface upside down. This process is suitable for assembling heterostructures for ARPES, where the top capping layer should be monolayer graphene. The laser-based micro-focused ARPES measurements of 5-layer WTe₂, 3-layer MoTe₂, 2-layer WTe₂/few-layer Cr₂Ge₂Te₆, and twisted double bilayer WTe₂ demonstrate that this process can be utilized as a versatile sample fabrication method for investigating the energy spectra of 2D heterostructures.