Optimized Fabrication Procedure for High-Quality Graphene-based Moiré Superlattice Devices

Abstract: Moir\'e superlattices constitute a versatile platform to investigate emergent phenomena arising from the interplay of strong correlations and topology, while offering flexible in situ tunability. However, the fabrication of such moir\'e superlattices is challenging. It is difficult to achieve highly uniform devices with a precise twist angle because of the unintentional introduction of heterostrain, twist angle disorder, and angle/lattice relaxation during the nanofabrication process. This article introduces an optimized, experience-informed protocol for fabricating high-quality graphene-based moir\'e superlattice devices, focusing on a modified dry transfer technique. The transfer process is performed in a highly tunable, custom-built transfer setup that enables precise position, angle, and temperature control. By combining rigorous flake selection criteria, pre-cleaned bubble-free bottom gates, and graphene laser ablation, the moir\'e superlattice is constructed by deliberately overlaying twisted graphene flakes at a submicron speed at room temperature. Through precise control of the transfer process, the resulting graphene moir\'e superlattice devices exhibit high uniformity and desired twist angles. This optimized protocol addresses existing challenges in the fabrication of graphene-based moir\'e superlattice devices and paves the way for further advances in the rapidly evolving field of moir\'e materials.