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

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 T_g . By utilizing the difference in T_g , a 2D heterostructure can be transferred from a high- T_g polymer to a lower- T_g 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 WTe 2 , 3-layer MoTe 2 , 2-layer WTe 2 /few-layer Cr 2 Ge 2 Te 6 , and twisted double bilayer WTe 2 demonstrate that this process can be utilized as a versatile sample fabrication method for investigating the energy spectra of 2D heterostructures.