High-yield fabrication of bubble-free magic-angle twisted bilayer graphene devices with high twist-angle homogeneity

Summary

Magic-angle twisted bilayer graphene (MATBG) is a very versatile material, hosting a wide variety of exotic phases while allowing easy tunability of material parameters. However, the fabrication of MATBG devices remains a challenging and inefficient manual process, with device properties being highly dependent on the specific fabrication methods, often resulting in inconsistency and variability. Here we present an optimized protocol for the fabrication of MATBG samples, using deterministic graphene anchoring to stabilize the twist angle and a careful bubble-removal technique to ensure high twist-angle homogeneity. We use low-temperature transport experiments to extract the average twist angle between pairs of leads. We find that up to ∼38% of the devices show μm²-sized regions with twist angles in the range of θ = 1.1 ± 0.1° and twist-angle variations of Δθ ≤ 0.02°. In some instances, such regions were up to 36 μm² large. The discussed protocols may be directly transferred to non-graphene materials and will be useful for the growing field of moiré materials.